A cyclist rides her bike at a rate of 8 meters per second. What is this rate in kilometers per hour? How many kilometers will the cyclist travel in 2 hours?

Question

I do not understand this. Can someone answer this soon and go through it step by step plz? Thank you!

Answer 1

Hi Raquel,

v = 8meters/sec , 1 meter = 1x10^-3 km

v=8x10^-3 km/sec,  

1sec = (1/60) minute, 1minute = 1/60 hr, therefore, 1 sec = (1/60)(1/60) hr = 1/3600 hr

1/sec = 3600/hr

v = 8x10^-3 km *3600/hr =28.8 km/hr

Distance = v*t = 28.8km/hr*2hr =57.6 km

Answer 2

We know that the cyclist rides her bike at 8 meters/second. However, the problem first wants to convert that speed to different units, namely km/hr. You can do this using what is called the factor ratio method.

 

(8 m/s)(1 km / 1000 m) (3600 s / 1 hr) = 28.8 km/hr

 

Each of these multiplying factors is like multiplying by 1. 1 km = 1000 m and 1 hr = 3600 s. When you multiply one of these factors, you want to do so with the unit that you want in the numerator and the unit you are trying to get rid of in the denominator so that undesirable unit cancels out.

 

For the second part of this problem, we assume that the cyclist travels at a constant speed. Then, we can use the distance formula

 

d = vt

 

where d is distance, v is speed and t is time.

 

d = (28.8 km/hr) (2 hr) = 57.6 km