Problem #21 asks
how much longer (percentage) is a one-mile race than a
1500-m race ("the metric mile")? I converted 1 mile to
meters----1mi=5280ft=1.609km---1.609km(10^3m/1km)=16090m,
but I am not sure what to do next.
1.609 * 10^3 = 1609, not 16090.
There is a common calculator error that could lead to that result, which would be to multiply 1.609 * 10 E3. E3 itself means 10^3, so if you multiply by 10 E3 you are multiplying by 10 * 10^3, which is 10^4.
I'm not sure that's the source of the error, but if it was: Naturally you will rely on a calculator to do a lot of your arithmetic, but to do this multiplication by a power of 10 you shouldn't rely on the calculator.
In any case the question comes down to the percent difference between 1500 m and 1609 m.
So the question becomes, what is the difference between 1500 and 1609, and what percent is that of 1500?