Extract mathThe sum of two consecutive integers is 15. Can I find the numbers if I know only the sum?

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hala718's profile pic

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

Posted on

Given two consecutive numbers.

Then we can assume that the first number is x.

Then the other number will be x+1.

We are given that the sum of the numbers is 15.

Then, we can write as follow:

x + ( x+ 1) = 15

==> x + x + 1 = 15

==> 2x + 1 = 15

Now we will subtract 1 from both sides.

==> 2x = 14

Now we will divide by 2.

==> x = 7

Then the first number is 7, and the other number is 8.

Then, 7 and 8 are two consecutive numbers whose sum is 15.

pohnpei397's profile pic

pohnpei397 | College Teacher | (Level 3) Distinguished Educator

Posted on

The answer is that the numbers are 7 and 8.  You can find this mathematically.

You know that they are consecutive so if the first number is x then the next number is x + 1.  So you could have the following equations:

x + y = 15

y = x + 1

x + X + 1 = 15

2x = 14

x = 7

y = 8

giorgiana1976's profile pic

giorgiana1976 | College Teacher | (Level 3) Valedictorian

Posted on

If the integers are consecutive, that means that one is odd and the other is even.

We'll put the numbers as a and a+1.

Their sum is 15:

a + a + 1 = 15

We'll combine like terms:

2a = 15 - 1

2a = 14

a = 7

The next integer number is a + 1 = 7 + 1 = 8

The consecutive integer numbers are: 7 and 8.

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