Question

You can ride a bicycle 15 mph. Your sister rides 12 mph. You give her a one hour head start. In how many hours will you catch up if neither of you stops?

Answer 1

Answer:

4 hours

Step-by-step explanation:

It is given you can ride a bicycle 15 mph. Your sister rides 12 mph. You give her a one hour head start.

Your info:

Speed = 15 mph , let the distance covered be = 'x' miles , time taken to cover the distance,

time = $\frac{d}{s}$ = $\frac{x}{15}$

Sister's info:

Speed = 12 mph , let the distance covered be = x miles, time taken to cover the distance of 'x' miles,

time = $\frac{d}{s} = \frac{x}{12}$

Equation:  

Sister's time - your time = 1

$\frac{x}{12}- \frac{x}{15} = 1$

Multiplying both the sides by 60 we get,

$5x -4 x = 60$

$x=60$ miles

Therefore, your time to catch up:

$\frac{x}{15}=\frac{60}{15}=4$ hours

Therefore, it will take 4 hours to catch up if neither of your stop.