1.

Average age of A and B 4 years ago was 20 years. Today, average age of A, B and C is 30 years. How old will C be 5 years from now?1. 55 years2. 50 years3. 40 years4. 47 years

Answer» Correct Answer - Option 4 : 47 years

Given:

Average age of A and B 4 years ago was 20 years.

Today, average age of A, B and C is 30 years.

Calculation:

Average age = Sum of ages of all individuals/Number of individuals

Calculation:

Let the age of A, B and C be x years, y years and z years respectively.

So, Four years ago the age of A and B is (x – 4) and (y – 4) respectively 

Now, four year ago the average age of A and B = (x – 4 + y – 4)/2

⇒ 20 = (x + y – 8)/2

⇒ x + y = 40 + 8

⇒ x + y = 48      ----(1)

Today, the average age of A, B and C is 30 years.

Average age = Sum of ages of all individuals/Number of individuals

⇒ 30 = (x + y + z)/3

⇒ x + y + z = 30 × 3 years

⇒ x + y + z = 90 years      ----(1)

Subtracting eq (1) from eq (2),

⇒ x + y + z - (x + y) = 90 – 48 years

⇒ z = 42 years

C's current age = z = 42 years

⇒ C's age 5 years from now = 42 + 5 years = 47 years

∴ C's age 5 years from now is 47 years.


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