It takes Bethany 8 hours to proof a chapter of Hawkes Learning Systems' Statistics book and it takes Nina 7 hours. How long would it take them working together? (Round your answer to two decimal places.)

Answer: it will take them 3.73 hours working together.

Step-by-step explanation:

It takes Bethany 8 hours to proof a chapter of Hawkes Learning Systems' Statistics book. This means that the rate at which she proofs a chapter per hour is 1/8

it takes Nina 7 hours. This means that the rate at which Nina proofs a chapter per hour is 1/7

If they work together, they would work simultaneously and their individual rates are additive. This means that their combined working rate would be

1/8 + 1/7 = 15/56

Assuming it takes t hours for both of them to proof a chapter working together, the working rate per hour would be 1/t. Therefore,

15/56 = 1/t

t = 56/15

t = 3.73 hours