Question

Kong took 15, percent fewer seconds than Nolan took to complete his multiplication timed test. Kong took 85 seconds.

Answer 1

Nolan took 100 seconds. Is what khan academy says.

Answer 2

Kong took 85 seconds to complete his multiplication timed test. Consider the proportion:

Nolan took x seconds - 100%

Kong took 85 seconds - 100%-15%=85%

That is mathematically

`(x)/(85)=(100)/(85),\\ \\x=(100\cdot 85)/(85)=100\ seconds.`

Answer: Nolan took 100 seconds to complete the test.