(I'm Overwhelmed) Algebra Progress Quiz #6 (Version 2) Q13

GRE Quant Problem Solving
1

Hi everyone! Q13 of the algebra progress quiz 6 asks
”Charles works for a lawn mowing company. He can mow one lawn in 4040 minutes. How much faster must his mowing rate be per hour so that he can mow 1515 lawns in 77 hours?”

After finding the larger and the smaller rate, I subtracted the smaller from the larger and then divided this difference by the original smaller rate. However, in the solution they only compute the subtraction. Since the question asks “how much faster is the second compared to the first?”, shouldn’t we take the ratio of the difference to the original rate? Why is my approach considered wrong?

Thank you!

2

When they state how much faster per hour, they are asking for the difference not the percent increase.

If you were to compute a percent increase, then there are no units for the result of that calculation. Since percent increase = |difference|/smaller number, then the units of lawns/hour cancel in the numerator and denominator leaving no units.

The question asks per hour, so we must be looking at the difference, so subtract the smaller number from the bigger number.

1 Like
3

Thank you very much!