Question

I am thinking of a positive integer that is 3 less than 3 times another number. The product

of my number and Ihe other number is 90. What is my number?

Answer 1

15

Explanation:

Write an equation expressing the given relationship. Solve it to find the numbers.

__

setup

Let x represent "another number." Then the number I'm thinking of is ...

(3x -3)

and the product of that and "the other number" is 90:

x(3x -3) = 90

solution

x(x -1) = 30 . . . . . . divide by 3

We know the factors of 30 are ...

30 = 30·1 = 15·2 = 10·3 = 6·5

Of these factor pairs, the numbers that differ by 1 are 6 and 5. "The other number" is 6, and "my number" is 90/6 = 15.

My number is 15.