1.

1). 70 years2). 80 years3). 90 years4). 100 years

Answer»

Let the age of FATHER, MOTHER and son be 4x, 3x, x.

Then, Age of daughter = 6x/5

Age of Grandmother = 2 × 3x = 6x

Sum of ages of family = 4x + 3x + x + 6x/5 + 6x = 76x/5

⇒ 76x/5 = 45.6 × 5

⇒ x = 15

⇒ Age of grandmother = 15 × 6 = 90 YEARS



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