Oliver and Lenny started hiking a hill simultaneously from the bottom to the top. Oliver hiked at a speed of 5 km/h during the first half, then decreased his speed to 4 km/h during the second half. Lenny hiked at a speed of 4 km/h during the first half, then increased his speed to 5 km/h in the second half. Who reached the top of the hill first? What is the proportion of time he spent hiking to that of his friend?

Oliver and Lenny reached the top of the hill at the same time

The proportion of time Oliver spent hiking to that of Lenny is 1:1

Step-by-step explanation:

1. Let's review the information given to us to answer the question correctly:

Oliver's speed = 5 km/h during the first half, then decreased his speed to 4 km/h during the second half.

Lenny's speed = 4 km/h during the first half, then increased his speed to 5 km/h in the second half.

2. Who reached the top of the hill first? What is the proportion of time he spent hiking to that of his friend?

Let's assume the distance from the bottom to the top of the hill is 10 kilometers for calculating the time it will take Oliver and Lenny to reach the top of the hill:

Speed = Distance/Time

Time = Distance/Speed

Oliver = Time of hiking first 5 km + Time of hiking second 5 km

Lenny = Time of hiking first 5 km + Time of hiking second 5 km

Oliver = 5/5 + 5/4

Oliver = 1 + 5/4 = 2 1/4 hours

Lenny = 5/4 + 5/5

Lenny = 5/4 + 1 = 2 1/4 hours

Oliver and Lenny reached the top of the hill at the same time

The proportion of time Oliver spent hiking to that of Lenny is 1:1