Question

Rising Grade 9: Lesson 9Story Problem Lesson 9:As part of a competition, Diego must spin around in a circle 6 times and then run to a tree. The time he spends on each spin is represented by s and the time he spends running is r. He gets to the tree 21 seconds after he starts spinning. If it takes Diego 1.2 seconds to spin around each time, how many seconds did he spend running?

Answer 1

13.8 s

Explanation:

According to the statement, we have the following:

The time to spin 6 times is represented as 6s since it does so 6 times and s is the time to spin. Then the total time it took to reach the tree, which would be the sum of the time of the spins plus the running time, that is r, would be:

`6s+r=21`

We are told that s is equal to 1.2, so we calculate r like this:

`\begin{gathered} 6\cdot1.2+r=21 \\ \\ r=21-7.2 \\ \\ r=13.8\text{ }s \end{gathered}`

that is to say that the running time is equal to 13.8 seconds