Question

When Amy's CD'S are fully charged, it lasts for 9 hours. She only charged it 9/12 full, how long will it last?

Answer 1

6.75 hours.

Explanation:

Given:

Time lasted on full charge = 9 hours.

CD's charged by Amy =
`(9)/(12)` of full charge.

Using unitary method, we solve for the time the CD's will last for given charge.

This can be done by multiplying the time for 1 complete charge and the fraction of the charge done.

∵ Time required for 1 complete charge = 9 hours.

∴ Time required for
`(9)/(12)` of full charge =
`(9)/(12)* 9`

⇒ Time required for
`(9)/(12)` of full charge =
`(81)/(12)=6.75\ h`

Therefore, the time it will last for
`(9)/(12)` of full charge is 6.75 hours.