course Mth 174 This ends the first assignment.}ӟĭƊʔqY{{ۺfDž
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19:23:10 `q001. There are 11 questions and 7 summary questions in this assignment. What is the area of a rectangle whose dimensions are 4 m by 3 meters.
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RESPONSE --> To find the area of a rectangle, you use A=L * W: A=4 * 3 A= 12m^2 confidence assessment: 3
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19:23:47 A 4 m by 3 m rectangle can be divided into 3 rows of 4 squares, each 1 meter on a side. This makes 3 * 4 = 12 such squares. Each 1 meter square has an area of 1 square meter, or 1 m^2. The total area of the rectangle is therefore 12 square meters, or 12 m^2. The formula for the area of a rectangle is A = L * W, where L is the length and W the width of the rectangle. Applying this formula to the present problem we obtain area A = L * W = 4 m * 3 m = (4 * 3) ( m * m ) = 12 m^2. Note the use of the unit m, standing for meters, in the entire calculation. Note that m * m = m^2.
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RESPONSE --> self critique assessment: 3
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19:26:37 `q002. What is the area of a right triangle whose legs are 4.0 meters and 3.0 meters?
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RESPONSE --> To find the area of a triangle, use A=1/2 b * h. A= 1/2 (4.0) * (3.0) A= 1/2 (12) A= 6m^2 confidence assessment: 2
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19:27:10 A right triangle can be joined along its hypotenuse with another identical right triangle to form a rectangle. In this case the rectangle would have dimensions 4.0 meters by 3.0 meters, and would be divided by any diagonal into two identical right triangles with legs of 4.0 meters and 3.0 meters. The rectangle will have area A = L * W = 4.0 m * 3.0 m = 12 m^2, as explained in the preceding problem. Each of the two right triangles, since they are identical, will therefore have half this area, or 1/2 * 12 m^2 = 6.0 m^2. The formula for the area of a right triangle with base b and altitude h is A = 1/2 * b * h.
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RESPONSE --> self critique assessment: 3
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19:28:29 `q003. What is the area of a parallelogram whose base is 5.0 meters and whose altitude is 2.0 meters?
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RESPONSE --> To find the area of a parallelogram, use A= b*h A=5.0 * 2.0 A= 10.0m^2 confidence assessment: 2
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19:28:37 A parallelogram is easily rearranged into a rectangle by 'cutting off' the protruding end, turning that portion upside down and joining it to the other end. Hopefully you are familiar with this construction. In any case the resulting rectangle has sides equal to the base and the altitude so its area is A = b * h. The present rectangle has area A = 5.0 m * 2.0 m = 10 m^2.
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RESPONSE --> self critique assessment: 3
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19:30:12 `q004. What is the area of a triangle whose base is 5.0 cm and whose altitude is 2.0 cm?
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RESPONSE --> To find the area of a triangle use A=1/2b*h A=1/2 (5.0) * (2.0) A= 1/2 (10.0) A=5.0cm^2 confidence assessment: 2
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19:30:22 It is possible to join any triangle with an identical copy of itself to construct a parallelogram whose base and altitude are equal to the base and altitude of the triangle. The area of the parallelogram is A = b * h, so the area of each of the two identical triangles formed by 'cutting' the parallelogram about the approriate diagonal is A = 1/2 * b * h. The area of the present triangle is therefore A = 1/2 * 5.0 cm * 2.0 cm = 1/2 * 10 cm^2 = 5.0 cm^2.
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RESPONSE --> self critique assessment: 3
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19:38:00 `q005. What is the area of a trapezoid with a width of 4.0 km and average altitude of 5.0 km?
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RESPONSE --> The area of a trapezoid is A=1/2 h(b1 + b2) when h is height, b1 is base1 and b2 is base2. Here we only know the width. A= 1/2 (5.0) (4.0 +2.0) A= 1/2(5.0)(6.0) A=1/2(30.0) A=15km^2 confidence assessment: 0
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19:40:20 Any trapezoid can be reconstructed to form a rectangle whose width is equal to that of the trapezoid and whose altitude is equal to the average of the two altitudes of the trapezoid. The area of the rectangle, and therefore the trapezoid, is therefore A = base * average altitude. In the present case this area is A = 4.0 km * 5.0 km = 20 km^2.
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RESPONSE --> Since both bases weren't given, use the average altitude to multipy with the base. self critique assessment: 2
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19:42:59 `q006. What is the area of a trapezoid whose width is 4 cm in whose altitudes are 3.0 cm and 8.0 cm?
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RESPONSE --> A=1/2h (b1 + b2) A=1/2 (4) (3.0 + 8.0) A= 1/2(4)(11) A= 1/2 (44) A= 22cm^2 confidence assessment: 1
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19:43:17 The area is equal to the product of the width and the average altitude. Average altitude is (3 cm + 8 cm) / 2 = 5.5 cm so the area of the trapezoid is A = 4 cm * 5.5 cm = 22 cm^2.
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RESPONSE --> self critique assessment: 2
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19:44:55 `q007. What is the area of a circle whose radius is 3.00 cm?
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RESPONSE --> The area of a circle is A= pi r^2 so, A= pi (3.00)^2 A= 9pi cm^2 confidence assessment: 3
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19:46:05 The area of a circle is A = pi * r^2, where r is the radius. Thus A = pi * (3 cm)^2 = 9 pi cm^2. Note that the units are cm^2, since the cm unit is part r, which is squared. The expression 9 pi cm^2 is exact. Any decimal equivalent is an approximation. Using the 3-significant-figure approximation pi = 3.14 we find that the approximate area is A = 9 pi cm^2 = 9 * 3.14 cm^2 = 28.26 cm^2, which we round to 28.3 cm^2 to match the number of significant figures in the given radius. Be careful not to confuse the formula A = pi r^2, which gives area in square units, with the formula C = 2 pi r for the circumference. The latter gives a result which is in units of radius, rather than square units. Area is measured in square units; if you get an answer which is not in square units this tips you off to the fact that you've made an error somewhere.
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RESPONSE --> self critique assessment: 3
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19:48:13 `q008. What is the circumference of a circle whose radius is exactly 3 cm?
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RESPONSE --> To find the circumference of a circle, use C= pi d or C= pi (r*2) C=pi (3*2) C=6pi cm^2 confidence assessment: 2
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19:49:30 The circumference of this circle is C = 2 pi r = 2 pi * 3 cm = 6 pi cm. This is the exact area. An approximation to 3 significant figures is 6 * 3.14 cm = 18.84 cm. Note that circumference is measured in the same units as radius, in this case cm, and not in cm^2. If your calculation gives you cm^2 then you know you've done something wrong.
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RESPONSE --> I should not have squared the cm in the answer because the circumference is measured in the same units as radius. self critique assessment: 2
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19:51:49 `q009. What is the area of a circle whose diameter is exactly 12 meters?
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RESPONSE --> To find the area of a circle use A=pi r^2. Since the diameter is given, you can just divide it by 2 to get the radius. radius=6 A=pi (6)^2 A=36pi m^2 confidence assessment: 2
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19:52:24 The area of a circle is A = pi r^2, where r is the radius. The radius of this circle is half the 12 m diameter, or 6 m. So the area is A = pi ( 6 m )^2 = 36 pi m^2. This result can be approximated to any desired accuracy by using a sufficient number of significant figures in our approximation of pi. For example using the 5-significant-figure approximation pi = 3.1416 we obtain A = 36 m^2 * 3.1416 = 113.09 m^2.
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RESPONSE --> self critique assessment:
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19:55:30 `q010. What is the area of a circle whose circumference is 14 `pi meters?
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RESPONSE --> Since C=pi(diameter), the diameter is 14, which means the radius is 7. You can then find the area. A=pi r^2 A=pi (7)^2 A=49pi m^2 confidence assessment: 2
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19:55:53 We know that A = pi r^2. We can find the area if we know the radius r. We therefore attempt to use the given information to find r. We know that circumference and radius are related by C = 2 pi r. Solving for r we obtain r = C / (2 pi). In this case we find that r = 14 pi m / (2 pi) = (14/2) * (pi/pi) m = 7 * 1 m = 7 m. We use this to find the area A = pi * (7 m)^2 = 49 pi m^2.
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RESPONSE --> self critique assessment: 3
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20:01:06 `q011. What is the radius of circle whose area is 78 square meters?
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RESPONSE --> A=pi r^2 pi= 3.14 so 78 / 3.14= 24.8, which is r^2. The square root of 25 is 5. The radius is 5m confidence assessment: 2
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20:01:25 Knowing that A = pi r^2 we solve for r. We first divide both sides by pi to obtain A / pi = r^2. We then reverse the sides and take the square root of both sides, obtaining r = sqrt( A / pi ). Note that strictly speaking the solution to r^2 = A / pi is r = +-sqrt( A / pi ), meaning + sqrt( A / pi) or - sqrt(A / pi). However knowing that r and A are both positive quantities, we can reject the negative solution. Now we substitute A = 78 m^2 to obtain r = sqrt( 78 m^2 / pi) = sqrt(78 / pi) m.{} Approximating this quantity to 2 significant figures we obtain r = 5.0 m.
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RESPONSE --> self critique assessment: 3
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20:02:41 `q012. Summary Question 1: How do we visualize the area of a rectangle?
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RESPONSE --> To visualize the area of a rectangle you visualize blocks that are 1m/1m that make up the measurement. The area is the total number of blocks within the rectangle. confidence assessment: 2
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20:03:00 We visualize the rectangle being covered by rows of 1-unit squares. We multiply the number of squares in a row by the number of rows. So the area is A = L * W.
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RESPONSE --> A= L * W self critique assessment: 2
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20:03:42 `q013. Summary Question 2: How do we visualize the area of a right triangle?
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RESPONSE --> To visualize the area of a right triangle, you visualize it as part of a rectangle. You can then take the area of the rectangle and divide it in half. confidence assessment: 3
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20:03:55 We visualize two identical right triangles being joined along their common hypotenuse to form a rectangle whose length is equal to the base of the triangle and whose width is equal to the altitude of the triangle. The area of the rectangle is b * h, so the area of each triangle is 1/2 * b * h.
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RESPONSE --> self critique assessment: 2
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20:04:22 `q014. Summary Question 3: How do we calculate the area of a parallelogram?
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RESPONSE --> To calculate the area of a parallelogram you use A= L * W confidence assessment: 3
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20:04:34 The area of a parallelogram is equal to the product of its base and its altitude. The altitude is measured perpendicular to the base.
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RESPONSE --> self critique assessment: 3
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20:05:53 `q015. Summary Question 4: How do we calculate the area of a trapezoid?
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RESPONSE --> To calculate the area of a trapezoid you add the two altitudes, and multiply the sum by the base. confidence assessment: 2
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20:06:31 We think of the trapezoid being oriented so that its two parallel sides are vertical, and we multiply the average altitude by the width.
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RESPONSE --> You multiply the average altitude by the width, not the base, when you visualize the trapezoid as vertical. self critique assessment: 2
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20:07:12 `q016. Summary Question 5: How do we calculate the area of a circle?
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RESPONSE --> A= pi r^2 You can find the radius by dividing the diameter by 2. confidence assessment: 3
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20:07:21 We use the formula A = pi r^2, where r is the radius of the circle.
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RESPONSE --> self critique assessment: 3
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20:09:25 `q017. Summary Question 6: How do we calculate the circumference of a circle? How can we easily avoid confusing this formula with that for the area of the circle?
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RESPONSE --> You calculate the circumference of a circle with C=pi * diameter or C=pi (r *2). You can avoid comfusing this with finding the area of a circle because the circumference is measured in single units and area is measured in units squared. Also, when finding C you multiply r with 2 and when finding A you square 2. confidence assessment: 3
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20:09:42 We use the formula C = 2 pi r. The formula for the area involves r^2, which will give us squared units of the radius. Circumference is not measured in squared units.
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RESPONSE --> self critique assessment: 3
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20:10:47 `q018. Explain how you have organized your knowledge of the principles illustrated by the exercises in this assignment.
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RESPONSE --> I have organized my knowledge of the principles illustrated by the exercises in this assignment by writing down each problem, the correct answers, and ways of solving them. confidence assessment: 3
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