Problem Solving

I am really struggling with these types of problems....

At his hourly rate, Don had estimated the labor cost of a repair job as $336 and was paid that amount. However, the job took 4 hours longer than he had estimated and, consequently, he earned $2.00 per hour less than his regular hourly rate. What was the time Don had estimated for the job, in hours?

That is fantastic Anju. I really appreciate you showing me a much simpler approach than the book. I just get really stuck tryng to work out how to answer questions like these and waste 5-10minutes on them...

Is there any special approach I should be adopting?

At his regular hourly rate, Don had estimated the labor cost of a repair job as $336 and he was paid that amount. However, the job took 4 hours longer than he had estimated and, consequently, he earned 2$ per hour less than his regular hourly rate. What was the time Don had estimated for the job, in hours?

28
24
16
14
12

We can plug in the answers, which represent the estimated time: 28, 24, 16, 14, or 12.
The actual time was 4 hours longer: 32, 28, 20, 18, or 16.
Since 336 is not a multiple of 32, eliminate A.
Since 336 is not a multiple of 20, eliminate C.
336 is not a multiple of 9, since the sum of its digits is not a multiple of 9.
Thus, 336 is not a multiple of 18; eliminate D.

The correct answer must be B or E.

Answer choice B: estimated time = 24, actual time = 28
Estimated payrate = 336/24 = 14.
Actual payrate = 336/28 = 12.
Difference = 14-12 = 2.
Success!

The correct answer is B.

Note that we had to try only ONE answer choice -- a very efficient way to solve the problem.