Chapter 7.2, Problem 20E

a.

To determine

To calculate: the number of cars in race.

Answer to Problem 20E

There were $30$ cars in the race

Explanation of Solution

Given information: the question is

When three cars in the race weighed less than $600$ pounds. These cars made up $10\%$ of all the cars.

Calculation:

  $\frac{10}{100}$ of all cars $=3$

  $\begin{array}{l}\frac{10}{100}=\frac{3}{x}\\ \frac{10}{100}\times \frac{100}{10}\times x=3\times \frac{100}{10}\\ x=\frac{300}{10}\\ x=30\end{array}$

b.

To determine

To calculate: the percent of three wheeled car.

Answer to Problem 20E

The percent of three wheeled car is $53.33\%$

Explanation of Solution

Given information: the question is

When there are $16$ three wheeled cars

Calculation: The percent of three wheeled car,

  $\begin{array}{l}\frac{16}{30}=\frac{x}{100}\\ \frac{16}{30}\times 100=\frac{x}{100}\times 100\\ x=\frac{160}{3}\\ x=53.33\%\end{array}$

c.

To determine

To calculate: the number of cars can complete the course.

Answer to Problem 20E

There are $12$ cars completed the course

Explanation of Solution

Given information: the question is

When the course was $2247.39$ miles long, and it was completed $40\%$ by of the cars

Calculation: The numbers of cars can completed their course,

  $\begin{array}{l}\frac{40}{100}=\frac{x}{30}\\ \frac{40}{100}\times 30=\frac{x}{30}\times 30\\ x=\frac{2\times 30}{5}\\ x=12\end{array}$