The Number Game

Algebra Level 2

The product of three consecutive numbers when divided by each of them in turn, the sum of three quotients will be 74. What is the first number?


The answer is 4.

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1 solution

Aryan Gaikwad
Feb 28, 2015

Let the first number be x x . Therefore the the three consecutive numbers will be x , x + 1 , x + 2 x, x+1, x+2 .

Product of the three consecutive numbers = x ( x + 1 ) ( x + 2 ) = x(x+1)(x+2)

Given,

x ( x + 1 ) ( x + 2 ) x + x ( x + 1 ) ( x + 2 ) x + 1 + x ( x + 1 ) ( x + 2 ) x + 2 = 72 ( x + 1 ) ( x + 2 ) + x ( x + 2 ) + x ( x + 1 ) = 72 3 x 2 + 6 x 72 = 0 x 2 + 2 x 24 = 0 \frac { x(x+1)(x+2) }{ x } +\frac { x(x+1)(x+2) }{ x+1 } +\frac { x(x+1)(x+2) }{ x+2 } =72\\ (x+1)(x+2)\quad +\quad x(x+2)\quad +\quad x(x+1)=72\\ 3{ x }^{ 2 }+6x-72=0\\ { x }^{ 2 }+2x-24=0

On solving the quadratic equation, we see that x = 4 x = 4 or x = 6 x = -6 . But since the sum of the equation given above is positive, x = 4 x=4 .

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