Question

List all the pairs of integers with a product of 36. then find the pair whose sum is 20

Answer 1

This is an excellent practice for the solution of quadratic equations.

1*36=36 => (1,36)
2*18=36 => (2,18)
3*12=36 => (3,12)
4*9=36 => (4,9)
6*6=36 => (6,6)
9*4=36 => (9,4)
12*3=36 => (12,3)
18*2=36 => (18,2)
36*1=36 => (36,1)

We can see that the sum decreases until the two factors are close (or equal) and then increases again.

The pair of integers with a sum of 20 is therefore (2,18) or (18,2).

Answer 2

Answer: It must be (18,2) or (2,18).

Explanation:

Since we have given that

The product of pairs of integers = 36

So, pairs must be

(1,36)

(2,18)

(3,12)

(4,9)

(6,6)

(9,4)

(12,3)

(18,2)

(36,1)

But we need the pair of integers whose sum is 20.

So, it must be (18,2) or (2,18).