Question

Dori and Malory are tracking their steps taken as a health goal. Dori leaves her house at 12:00 p.m. and walks at 50 steps per minute. Malory leaves her house at 12:20 p.m. and walks at 90 steps per minute. At what time will Malory's steps catch up to Dori's steps?

Answer 1

Let n = minutes since 12:00 pm when Malory catches up to Dori.

Dori travels
(50 steps/min)*(n minutes) = 50n steps

Malory begins walking at 12:20 pm, so she walks for (n - 20) minutes. She travels
(90 steps/min)*(n - 20  min) = 90n - 1800 steps

Equate the steps traveled by Dori and Malory.
90n - 1800 = 50n
40n = 1800
n = 45 min

The time corresponding to n = 45 min is 12:45 pm

Answer: 12:45 pm