Jenine can sharpen a pencil 5 times before it runs out. She needs to sharpen a pencil for every 1.5 hours of use. She already has ten pencils and needs to write for 105 hours. A new pencil costs $2. How much does she need to spend on more pencils to be able to write for 105 hours?
Let’s work this out in a step by step way to be sure we have the right answer.
8
A pencil last 7.

5 hours because 5 x 1.

5 = 7.

5.

The pencils she has will last 75 hours because 10 x 7.

5 = 75.

She needs 30 more hours of writing because 105 - 75 = 30.

She will need 4 more pencils to reach this because 30 / 7.

5 = 4.

She will spend $8 on pencils because 4 x 2 = 8.

.

The final answer: 8