Given:

Time needed for each to build alone = 16 hrs.

Don works at 8

Ric workds at 8:30

Mike works at 9:00

Required:

Time they finished the boat (T).

Solution.

If T is the time they all finish the boat, then, the total hours of work for the workers are:

Don works (T -8) hours.

Ric works (T-8.5) hours.

Mike workds (T-9) hours.

The works done for each in an hour = `1/16` of the boat.

==> Now we will find the work done at T hour for each.

Don = `(T-8)*1/16 `

`` Ric = (`T-8.5)*1/16 `

`` Mike = `(T-9) * 1/16`

`` Then the total will be the finished boat = 1.

==> `(T-8)/16 + (T-8.5) /16 + (T-9)/16 = ` 1

==> T-8 + T- 8.5 + T-9 = 16

==> 3T -25.5 = 16

==> 3T = 41.4

==> T = `41.4/3` = 13.8

Now we will convert to Time.

13 = 1 pm

0.8 = 0.8*60= 48 min.

**Then , the time they finished the boat is 13:48 OR 1:48.**