How do i approximate a square root

The calculus approach is to use Newtons Method:

where 

Start with initial guess of "a".
After 4 or 5 iterations, you should get a close approximation to 
...............

If you wanted a non-calculus approach, I would suggest divide and conquer.
First determine which 2 integers the sqrt lies in between by perfect squares.

Then use midpoint  for next guess, if 

then repeat with "m" = midpoint. Otherwise repeat with "n" = midpoint.
Continue until you have a good approximation, about 6-8 decimal points.

Ithink you're supposed to multiply 12.50 which is how much he makes per hour and then multiply it by each number then add whats left togrther and there's your answer