To find an average of quantities of the same kind is to add all the items together and then divide the sum by the number of items.
1 of 3 〉 The average weight of A, B and C is 45 kg, that of A and B is 40 kg and B and C is 43 kg. What is the weight of B?
2 of 3 〉 The average of following 5 numbers is 8, find the missing number in 7, 5, 3,12,?.
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