Question

Sam left his school at 3:05. He walked at a speed of 3.2 mph. 15 minutes later, Al started running after him, and he caught up with Sam 10 minutes later. What was Al’s speed?

Answer 1

Answer: 8 miles per hour (mph)

Step by step explanation:  

Given that,

Sam left his school at 3:05

Walked at a speed of 3.2 mph

Al’s speed = ?

AI caught up with Sam 10 minutes later

Speed = distance /time

Sam’s distance  

3.2 x 1/4 = 0.8 miles

At the same time, Al runs for 10 min, which is 1/6 hr.  

Meanwhile in the same 10 minutes, Sam walks 3.2 x 1/6 =0.53 miles.

AI ran the distance of -> 0.8+ 0.53 = 1.3 miles  

According to the above formula  

1/3 divided by 1/6 = 4/3  

4/3 * 6 = 24/3 = 8 mph

 

Answer 2

At 3:05 sam left for his school at speed of 3.2 miles per hour.
After 15 minutes, thus, around 3:20, Al started running after him.
AL caught up after 10 minutes later.
Als speed
=> 3.2 mph * 60 minutes = 192 miles per minute
=> 192 miles per minute / 15 = 12.8  miles

12.8 miles /10 minutes = 1.28 miles per hour is Als speed.