Question 1 The average weight of 10 girls is 77lbs. If the youngest girls is excluded, the average weight changes to 78 lbs. What is the weight in lbs of the youngest girl?

-- Answer -- 68

77 * 10 = 770, 770 – x / 9 = 78 770 – x = 78 * 9 = 702, 770 – 702 = x = 68

Question 2 To increase the mean of 4 numbers by 3, how much would the sum of 4 number have to increase?

-- Answer -- avg + 3

(x + x + x + x) / 4 + 12 / 4 = avg + 3