1.

The ratio of ages of two persons A and B is 3∶ 4 and that of ages of B and C is 4∶ 5. If the average of all three is 40 years. What is B's age?1. 20 years2. 30 years3. 40 years4. 50 years

Answer» Correct Answer - Option 3 : 40 years

Given:

Average age = 40 years

Formula used:

Average = Sum of all the terms/Total number of terms

Calculation:

A∶ B =3∶ 4

And, B∶C =4∶5

Then, A∶ B∶ C = 3∶ 4∶ 5

Let the age of A, B and C be 3x, 4x and 5x

Sum of ages of all the persons = 3x + 4x + 5x = 12x

Average = 12x/3 = 4x

⇒ 4x = 40

⇒ x = 10

∴ The age of B is 40



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