Two numbers are such that the first is half as large as the other. If the sum of the two numbers is 720, what are the numbers?

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justaguide's profile pic

justaguide | College Teacher | (Level 2) Distinguished Educator

Posted on

Let the number we need to find be x and y.

The sum of the numbers is x + y = 720...(1)

We also know that one number is half the other. x = y/2

substitute y = 2x in equation (1)

x + y = 720

=> x + 2x = 720

=> 3x = 720

=> x = 720/3

=> x = 240

y = 2*x = 480

This gives the two numbers as 240 and 480.

hala718's profile pic

hala718 | High School Teacher | (Level 1) Educator Emeritus

Posted on

Let the first number be x and the second number be y.

Given that x is half y

==> x = y/2 .............(1)

Also, given that the sum of the numbers is 720.

==> x + y = 720.............(2)

Now we will substitute (1) into (2).

==> (y/2) + y = 720

We will multiply by 2.

==> y+ 2y = 1440

==> 3y = 1440

Now we will divide by 3.

==> y= 1440/3 = 480

==> y= 480

==> x= 480/2 = 240

Then the numbers are 480 and 240.

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