Question

Xanthia can read 100 pages per hour and Molly can read 50 pages per hour. If they each read the same book, and the book has 225 pages, how many more minutes than Xanthia would it take for Molly to finish reading the book?

Answer 1

135 mins

Explanation:

Reading the book takes Xanthia

$\frac{225}{100}=2.25$ hours.

It takes Molly

$\frac{225}{50}=4.5$ hours.

The difference is $2.25$ hours, or $2.25(60)=\boxed{135}$ minutes.

Answer 2

135 minutes

Explanation:

Let

y -----> the number of pages to finish reading the book

x ----> the number of hours

we know that

The linear equation in slope intercept form is equal to

`y=mx+b`

where

m is the unit rate or slope of the linear equation

b is the y-intercept or initial value

In this problem we have

Xanthia

`m=100\ pages/hour`

`b=225\ pages`

`y=-100x+225` ----> the slope is negative because is a decreasing function

For y=0

substitute and solve for x

`0=-100x+225`

`100x=225`

`x=2.25\ hours` ---> Xanthia's time to finish reading the book

Molly

`m=50\ pages/hour`

`b=225\ pages`

`y=-50x+225` ----> the slope is negative because is a decreasing function

For y=0

`0=-50x+225`

`50x=225`

`x=4.5\ hours` --- Molly's time to finish reading the book

To find out how many more minutes than Xanthia would it take for Molly to finish reading the book, subtract Xanthia's time from Molly's time

`4.5\ h-2.25\ h=2.25\ h`

Convert to minutes

Multiply by 60

`2.25\ h=2.25(60)=135\ minutes`