Question

when I divide 3 and then add 5 my answer is twice the number I thought of find the number

Answer 1

Let the number be x

x/3 + 5 = 2x

Take away x/3 from both sides:

5 = 2x - x/3

Combine like terms:

5/3 x = 5

Multiply by 3 on both sides:

5x = 15

Divide both sides by 5:

x = 3

Answer: The number is 3

Answer 2

Let the required number be x,

According to the given information,

( 3 / x ) + 5 = 2 x

=> ( 3 + 5x ) / x = 2x

=> 3 + 5x = 2x^2

=> 2x^2 - 5x - 3 = 0

=> 2x^2 - ( 6 - 1 ) x - 3 = 0

=> 2x^2 - 6x + x - 3 = 0

=> 2x( x - 3 ) + ( x - 3 ) = 0

=> ( x - 3 )( 2x + 1 ) = 0

By Zero Product Rule,

x = 3 Or x - 1/2

taking + value, x = 3

Hence, the number which you thought was 3.