Use the z-score:
112 - 100
For 112, the z-score is --------------- = 12/15, or 0.8.
15
Next, find the AREA under the standard normal curve TO THE LEFT OF 0.8.
Use either a z-score table or a calculator for this purpose.
Using my calculator, I found that this area is 0.532. That places 112 in the 53rd percentile.
82 would be in a lower percentile: the 12th percentile.
Let me know if you have questions about how to use a calculator to do these calculations.
