To find the answer to "What two numbers have a product of 91 and a sum of 80?" we first state what we know. We are looking for x and y and we know that x • y = 91 and x + y = 80.
Before we keep going, it is important to know that x • y is the same as y • x and x + y is the same as y + x. The two variables are interchangeable. Which means that when we create one equation to solve the problem, we will have two answers.
To solve the problem, we take x + y = 80 and solve it for y to get y = 80 - x. Then, we replace y in x • y = 91 with 80 - x to get this:
x • (80 - x) = 91
Like we said above, the x and y are interchangeable, therefore the x in the equation above could also be y. The bottom line is that when we solved the equation we got two answers which are the two numbers that have a product of 91 and a sum of 80. The numbers are:
1.15415
78.84585
That's it! The two numbers that have a product of 91 and a sum of 80 are 1.15415 and 78.84585 as proven below:
1.15415 • 78.84585 ≈ 91
1.15415 + 78.84585 = 80
Note: Answers are rounded up to the nearest five decimals if necessary so the answers may not be exact.
Product Sum Calculator
Need the answer to a similar problem? Submit another product and sum below to find the two numbers that make your product and sum.