Question

Byron is 3 years older than Doug. The product of their ages is 40. How old Doug?

A. 10
B. 8
C. 5
D. 4

Answer 1

Option B is correct

Explanation:

Doug is x years old, so Byron is x+3 years old. The product of their ages would then be x times x+3:

x(x+3) = 40

x2 + 3x = 40

x2 + 3x + 40 = 0

Now, factor the equation:

(x+8)(x-5) = 0

Then, solve for both values of x:

x+8 = 0

x = -8

x-5 = 0

x = 5

As no one can have a negative age, we simply disregard x=-8 as invalid. Therefore, Doug is 5 years old & Byron must be 5+3 - or 8 years old.

Hope it is helpful...

Answer 2

Doug is 10 years old; option A

Explanation:

set up expressions using the information you already know:

B (byron)

D (doug)

B = D + 3

B * D = 40

you can now solve by plugging in an expression for the variable B in the second equation.

D + 3 * D = 40

D + 3D = 40

(combine like terms)

4D = 40

(divide by 4 on both sides to isolate the variable and balance the equation)

4D/4 = 40/4

D = 10

So, the answer is A; Doug is 10 years old