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  1. The average of three numbers is 77. The first number is twice the second and the second number is twice the third. The first number is :
    1. 33
    2. 66
    3. 77
    4. 132
Correct Option: D

Let the third number = p
∴ Second number = 2p
First number = 4p
The average of three numbers = 77
Now, p + 2p + 4p = 3 × 77
⇒ 7p = 3 × 77

⇒ p =
3 × 77
= 33
7

∴ First number = 33 × 4 = 132
Second method to solve this question with the help of given formula :
Here, a = 2, b = 2, X = 77
First number =
3ab
× X
1 + b + ab

First number =
3 × 2 × 2
× 77
1 + 2 + 2 × 2

First number =
12
× 77
7

First number = 12 × 11 = 132



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