The average of six numbers is 18.2. Four of the numbers are each decreased by five, while two of the numbers are each increased by eight. What is the average of the new set?
For these kinds of problems, we can see that the total, is 18.2*6 = 109.2 Four numbers are decreased by 5, -20 are increased by 8, so +16, so the net total is -4, which is 105.2, and 105.2/6 = 17.53333333333...
