The sum of two numbers is 70

Question

the sum of two numbers is 70. The first number is 2/5 of the second number . What are the numbers?

Answer 1

You may assign either one or two variables to the numbers:

    x = first number = (2/5)y

    y = second number

 

"sum of two numbers is 70"   means

          x + y = 70

     (2/5)y + y = 70

    2y + 5y = 350          [multiply everything by 5 to get rid of fraction]

        7y = 350             [collect terms]

          y = 50               [divide both sides by 7]

 

Then,

         x = (2/5)(50)

         x = 20

 

Check:

     Is  20 + 50 = 70   ?

              70 = 70   ?yes

     Is  20 = (2/5)(50)   ?

           20 = 20   ?yes