My son has saved $55 and is planning to save $3.50 each week from his allowance how long will it take him to have $111 to buy the cd player he wants

Question

He has 55 dollors he is gonna save 3.50 dollars each week he needs to get to 111 dollors 

Answer 1

To set up: 

Start with $55 which he already has and add $3.5*x (which is the unknown you are trying to find) and make it equal to $111

 

55 + 3.5x = 111

-55              -55    Subtract 55 from each side to isolate x on one side of the equation

 

        3.5x  = 56      You are left with 3.5x = 56 (the difference between what he needs and what he has)

        3.5       3.5     Divide each side by 3.5 to get x alone

 

            x   =  16     56/3.5 is equal to 16 

 

Meaning that it should take him 16 weeks to save up the additional money that he needs to get the CD player that he wants.

 

To double check your work:

 

$55 + ($3.5 * 16) = $111

 

$55 + ($56) = $111