The number a is 5 times as large as b. The sum of a and b is 18. What is the value of the product ab? Express your answer as a common fraction.
a ==5b..............(1)
a + b ==18........(2), solve for a, b
From (2) above:
a ==18 - b
Sub this in (1) above:
18 - b ==5b
18 ==5b + b==6b
b==18 / 6 ==3
a ==18 - 3 == 15
a * b ==3 * 15 ==45
