Question

Keith bought a rechargeable digital pen for his tablet. The digital pen uses 35 of a cell’s power each hour. How many hours will the digital pen work with 3 cells?

Answer 1

Explanation:

Every hour, it uses 35 of a cell's power.

So, we can write the ratio for the hours to the amount used as 1:35

Using the direct proportion, if one increase/decrease, the other one increase/decrease the same amount

Call the hours that the pen will work with 3 cells, x

1:35 = x:3

Divide the left side by 35/3

3/35 : 3 = x:3

x = 3/35

So, the pen will work 3/35 hours with 3 cells.