finding average

Question

^{the weight of eah pair of boy from a group of five was recorded. The foll. results were obtained 90kg,92kg, 93kg, 94kg, 95kg,96kg, 97kg, 98kg,100kg,101kg> what is the total weight of the five boys?}

Answer 1

Let wts of 5 boys be x1, x2, x3, x4, x5

 

x1 + x2 = 90

x1 + x3 = 92

x1 + x4 = 93

x1 + x5 = 94

x2 + x3 = 95

x2 + x4 = 96

x2 + x5 = 97

x3 + x4 = 98

x3 + x5 = 100

X4 + x5 = 101

 

Add all equations

 

4x1 + 4x2 + 4x3 + 4x4 + 4x5 = 956

 

Divide both sided by 4

 

x1 + x2 + x3 + x4 + x5 = 239 = wt of five boys

:)