Question

What number must be added to the set 7, 13, 20 and 8 to get an average of 12?

Answer 1

Let the number added be x.

After the addition of x, number of observations= 5

Average= Total/No of observations

12=7+13+20+8+x/5

12= 48+x/5

By cross multiplication

12×5=48+x

60=48+x

60-48=x

12 = x

So, the number added = 12 .

Answer 2

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Let,

The required number be x.

Average = 12 [ given ]

Set of numbers = 7, 13, 20, 8

After adding x to the set, we get

= 7 + 13 + 20 + 8 + x

= 48 + x

Total numbers = 5

Now,

Average = Sum of all numbers / Total numbers

12 = ( 48 + x ) / 5

48 + x = ( 12 ) ( 5 )

48 + x = 60

x = 60 - 48

x = 12

Hence,

The required number is 12.

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