Question

the mean of five numbers is 30.if one number is excluded, their mean becomes28.what was excluded number?

Answer 1

x1+x2+x3+x4+x5/5 =30
x1+x2+x3+x4+x5=30×5
x1+x2+x3+x4+x5=150
x1+x2+x3+x4/4 =28
x1+x2+x3+x4=28×4
x1+x2+x3+x4=112
substitute this in 1st equation
x1+x2+x3+x4+x5=150
112+x5=150
x5=150-112
x5=38
the excluded number is 38 is answer obtained

Answer 2

x1+x2+x3+x4+x5/5 =30

x1+x2+x3+x4+x5=30×5

x1+x2+x3+x4+x5=150

x1+x2+x3+x4/4 =28

x1+x2+x3+x4=28×4

x1+x2+x3+x4=112

substitute this in 1st equation

x1+x2+x3+x4+x5=150

112+x5=150

x5=150-112

x5=38