Question

Mean of 10 numbers is 55. If one number is included, their mean becomes 60. Find the included number.

Answer 1

Mean of 10 numbers = 55
sum of 10 numbers = 550

Now mean of 11 numbers = 60
sum of 11 numbers= 660
The number is 660-550 = 110

Answer 2

Given,

Mean of 10 numbers = 55

Total sum of 10 numbers = 55 * 10 = 550

Mean of ( 10 + 1 ) numbers = 60

Total sum of 11 numbers = 60 * 11 = 660

Now,

Included number = Total sum of 11 numbers - Total sum of 10 numbers

Included number = 660 - 550
=> Included number = 110