1. The mean of 7 numbers is 11. Five of the numbers are 3, 17, 20, 4 and 15.The remaining two numbers are each equal to y. Find(i) the sum of the 7 numbers,(ii) the value of y.

(i) The mean of a set of numbers is calculated by dividing the sum of the numbers by the quantity of numbers. In this case, the mean is 11 and there are 7 numbers, so the sum of the 7 numbers is 11 * 7 = 77.

(ii) To find the value of y, we first need to find the sum of the five given numbers, which is 3 + 17 + 20 + 4 + 15 = 59. Since the sum of all 7 numbers is 77, the sum of the two remaining numbers (which are both y) is 77 - 59 = 18. Since these two numbers are equal, we divide this sum by 2 to find the value of y, so y = 18 / 2 = 9.