A plumber charges $65 for a diagnostic check. After the check, it is $85 per hour for the work. With $320 in your wallet, how many hours of work san you afford?

1 Answer

4 hours, assuming any portion of an hour worked is charged out as another hour. 4.2 hours if that assumption doesn't hold.


We have $320 in the wallet:


And it costs $65 for the diagnostic check, so that means we pay that from our 320:


And the plumber charges $85/hr, so we divide that into the money we have left:

#355/85=4.2# hours, and since I'm going to assume that this problem will have our plumber charging us for an hour for any portion of that hour worked, we can have 4 hours of work done.

We can also approach this problem by writing out one algebraic equation. It would look like this:

#"diagnostic check" + "number of hours" xx "fee per hour" = "total fee"#, where #"total fee" < "cash in wallet"#

we can drop numbers into this:

#65 + nxx85 = "total fee"#, where #"total fee" < 320#

and so we can substitute in:

#65 + nxx85 = 320# to see the maximum n

and now we solve:


and then round down to the closest whole number, or 4.