Question

Nereo and Azeneth start recording video at the same time. Nereo's phone starts with
\[1{,}000\] megabytes (
\[\text{MB}\]) of free space and uses
\[7\,\text{MB}\] of space per second of video.
Azeneth's phone has
\[1{,}255\,\text{MB}\] of free space and uses
\[10\,\text{MB}\] of space per second of video.
How much free space will they have when they first have the same amount of space left?

Answer 1

Let t be seconds. Nereo: 1000 − 7t MB. Azeneth: 1255 − 10t MB.
Set equal: 1000 − 7t = 1255 − 10t → 3t = 255 → t = 85 s.
Remaining space = 1000 − 7·85 = 405 MB.