1.

The average of age of grandfather and grandmother is 65 years. If the age of granddaughter is included, the average of the three falls to 50. Find the age of granddaughter.1). 202). 103). 54). 15

Answer»

Let the age of grandfather and GRANDMOTHER is X and Y years and that of GRANDDAUGHTER is Z years.

According to question, the AVERAGE age of grandfather and grandmother is 65 years. i.e.

$(\Rightarrow \frac{{X + Y}}{2} = 65)$

⇒ X + Y = 130 years …..(1)

Also, Average age of G.father, G.mother and G.daughter is 50, thus

$(\Rightarrow \frac{{X + Y + Z}}{3} = 50)$

⇒ X +Y + Z = 150 …..(2)

Solving above two equations we get,

⇒ Granddaughter’s age, Z = 20 years


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