1.

The average of a group of numbers is 64. When a number is added to the group, the average becomes 70. When the number is again added to the group, the average is again increased to 75. Find the number.1). 702). 903). 1104). 130

Answer»

Let there be ‘n’ numbers in the group and the number to be added be ‘x’

Sum of numbers in group = 64n

When x is added to the group, sum of numbers in group = 70(n + 1)

⇒ 64n + x = 70(n + 1)

⇒ x = 70n + 70 – 64n

⇒ x = 6n + 70.... (1)

Now, when x is again added, sum of numbers in group = 75(n + 2)

⇒ 70(n + 1) + x = 75(n + 2)

⇒ 70n + 70 + x = 75n + 150

⇒ x = 5n + 80.... (2)

EQUATING (1) and (2),

⇒ 6n + 70 = 5n + 80

⇒ 6n – 5n = 80 – 70

⇒ n = 10

Substituting in eq. (1),

⇒ x = 6(10) + 70

⇒ x = 60 + 70 = 130

∴ The number is 130


Discussion

No Comment Found

Related InterviewSolutions