Question

Jack wants to save up money to buy his math teacher a new calculator for the holidays.After 4 weeks, he has $78 saved up. After 9 weeks, he has $138.How much money does Jack save per week?

Answer 1

$12 per week

Step-by-step explanation:

Let the time taken to save up the money be "x"

Let the amount saved up be "y "

If after 4 weeks, he has $78 saved up, this can be written in a coordinate form as (4, 78)

Similarly, if after 9 weeks, he has $138, this is written in a coordinate form as (9, 138)

To get the amount Jack saved per week, we will have to take the unit rate as shown below:

`\begin{gathered} m=(y_2-y_1)/(x_2-x_1) \\ m=(138-78)/(9-5) \\ m=(60)/(5) \\ m=12 \end{gathered}`

This shows that the amount of money that Jack save per week is $12 per week