Math Word Problems Demystified - A Self Teaching Guide

EVALUATION: Find the values of each and see if their sum is $1.25.

3 quarters¼ 3 $ 0 : 25 ¼$ 0 : 75

5 dimes¼ 5 $ 0 : 10 ¼$ 0 : 50

$ 0 : 75 þ$ 0 : 50 ¼$ 1 : 25

EXAMPLE:Bill is 8 years older than his brother. In 3 years, Bill will be twice

as old as his brother. Find their present ages.

SOLUTION:

GOAL: You are being asked to find the present ages of Bill and his brother.

STRATEGY: Let x¼Bill’s age

y¼his brother’s age

xþ 3 ¼Bill’s age in 3 years

yþ 3 ¼his brother’s age in 3 years

Since Bill is 8 years older than his brother, the first equation is

x¼yþ 8

In 3 years, Bill will be twice as old as his brother, so the second equation

is

xþ 3 ¼ 2 ðyþ 3 Þ

IMPLEMENTATION: Solve the system

x¼yþ 8

xþ 3 ¼ 2 ðyþ 3 Þ

LESSON 18 Using Two Equations 213