Question

The sum of two numbers is 8, and their product is 15. What is the largest number?

Answer 1

Hello there!

The sum of two numbers (x + y) is 8 (=8).
Their product (x * y) is 15 (=15).
x + y = 8
x * y = 15

First, we know that the two number must be positive and under 8, as the product is positive.

Let's list out some numbers that are from 1 to 8 that sum up to 8;
1 + 7
2 + 6
3 + 5
4 + 4

Now, we need to multiply the two numbers that add up to 8, and see which makes a product of 15.
1 * 7 = 7, this does not work.
2 * 6 = 12, this does not work.
3 * 5 = 15, this works!
4 * 4 = 16, this does not work.

Since we are looking for the larger number in our pairs, let's pick the largest one out of the correct pair, which is 5.

The largest number is 5.

I hope this helps!