Lisa is 3 times as old as a Maggie. The difference in their ages is 12 years. What are their ages?

Question

Lisa is 3 times as old as Maggie. The difference in their ages is 12 years. What are their ages? 

Answer 1

Hi Evan,

 

Let's call Lisa's age L and Maggie's age M:

 

We have

 

L = 3 times M or 3M and;

 

L - M = 12

 

Substituting the 3M for L (the first equation) into the L in the second equation gives us

 

3M - M =12

 

solving for M gives us

 

2M = 12 or M=6

since L = 3M, then L = 3 times 6 or 18

 

Lisa's age is 18 and Maggie's age is 6

Answer 2

Let x represent Maggie's age, then Lisa's age is 3x since Lisa is three times as old as Maggie. We know the difference between the girls ages is 12 years.

 

Create an equation using what we know, or 

 

Lisa's age - Maggie's age = 12 years.

 

  3x         -        x = 12 years

 

Combine the x terms:

 

                      2x = 12 years

 

Divide both sides by 2 giving:

 

                       x = 6 years

 

Then Maggie is 6 years old and Lisa is 18 years old or three times as old as Maggie.

 

Questions?