Question

7. Jeremy travels from his house to the Grill.
By what percent would the time taken by
him come down if he increased his average
speed by 20%?
(A) 10%
(B) 16%
(C) 20%
(D) 33%
(E) 80%​

Answer 1

By 16%, the time taken by  him come down if he increased his average  speed by 20%.

Let us consider the distance from Jeremy's house to the Grill be 200km and initially Jeremy goes at an average speed of 100km/hr.

So, the time taken by Jeremy to reach the Grill is = (Distance/Speed)

= (200km/100km/hr)

= 2 hours.

After his average speed increases by 20%, it becomes = (100+20)% of 100km/hr (Initial speed)

= 120% of 100km/hr

= 120 km/hr

So, the time taken would be = (Distance/New speed)

= 200km/120km/hr

= 1.667 hours

Percentage decrease in time = |(Final time - Initial time)/Initial time| ×100%

= |(1.667-2)/2|×100%

= 0.1667×100%

= 16.67%

≈ 16%

So, option (B) is correct.