Question

A cyclist rides her bike at a rate of 15 miles per hour. What is this rate in kilometers per hour? How many kilometers will the cyclist travel in 2 hours? In your computations, assume that I mile is equal to 1.6 kilometers. Do not round your answers.

Answer 1

1. 24 km/hour

2. 48 km

Explanation:

1 mile = 1.6 km

cyclist = 15 miles/ hour

we want to multiply speed by something that will cancel miles out and leave km. to do this, we want to multiply it by something with miles on the bottom and km on the top.

this is because

miles * km / miles = km as the miles cancel out and km is left in the numerator

thus,

1 mile = 1.6 km

divide both sides by 1.6 km to get 1 on a side

1 mile / 1.6 km = 1

alternatively, divide both sides by 1 mile to get 1 on a side

1.6 km / 1 mile = 1

since we want miles on the bottom, we choose the second option

cyclist = 15 miles / hour = 15 miles/hour * 1 = 15 miles/hour * 1.6km / 1 mile = 24 km /hour

24 km/hr for 2 hours = 24 km/hr * 2 hours = 24 * 2 km = 48 km