A boy speeds 4 miles down a mountain slope in 10 mins. What is his average speed in miles per hour (mph) over that time interval?

Question

I'm trying to solve these math problems and need a little.

Answer 1

If he travels 4 miles in 10 minutes, then he is going 4/10 miles/minute.  That simplifies to 2/5 miles/minute.  But you want miles per hour.  There are 60 minutes in 1 hour, so you need to decide if you're going to multiply or divide by the 60.  In order to cancel the minutes, I need to multiply by the 60.

2/5 x 60 = 24miles/minutes x minutes/hour= miles/hour

So the boy is going 24 miles per hour.

Answer 2

Hi Cassondra,

 

This problem involves a conversion from minutes to hours, which we can setup this way using our given speed ratio and our units conversion ratio:

    mph = (4 miles / 10 min.)(60 min. / hr.)

 

The minutes in the denominator of the 1st ratio and in the numerator of the 2nd ratio cancel each other out and we're left with mph:

   mph = (40 x 60) / 10 = 2400 / 10 = 24

 

Thanks for submitting this problem and glad to help.

 

God bless, Jordan.