Math Word Problems Demystified - A Self Teaching Guide

10. Will is 4 years older than Phil. Three years from now, Will will be
    twice as old as Phil was last year. Find their present ages.

SOLUTIONS:

1. Letx¼the son’s age and 6x¼the father’s age; thenxþ 9 ¼the son’s
   age and 6xþ 9 ¼the father’s age in 9 years.

3 ðxþ 9 Þ¼ 6 xþ 9

3 xþ 27 ¼ 6 xþ 9

3 x
 6 xþ 27 ¼ 6 x
 6 xþ 9

 3 xþ 27 ¼ 9

 3 xþ 27 
 27 ¼ 9 
 27

 3 x¼
 18

 31 x


 31

¼

18

3

x¼ 6 ðson’s ageÞ

6 x¼ 6  6 ¼ 36 ðfather’s ageÞ

2. Letx¼daughter’s age and 2x¼mother’s age; thenx
   20 ¼the
   daughter’s age and 2x
   20 ¼the mother’s age 20 years ago.

4 ðx
 20 Þ¼ 2 x
 20

4 x
 80 ¼ 2 x
 20

4 x
 2 x
 80 ¼ 2 x
 2 x
 20

2 x
 80 ¼
 20

2 x
 80 þ 80 ¼
 20 þ 80

2 x¼ 60

21 x

21

¼

60

2

x¼ 30 ðdaughter’s age)

2 x¼ 2  30 ¼ 60 ðmother’s age)

126 LESSON 12 Solving Age Problems