Math Word Problems Demystified - A Self Teaching Guide

Solve forx:

xþy¼ 20

xþ 5 ¼ 20

xþ 5 
 5 ¼ 20 
 5

x¼15 pounds

Hence, 15 pounds of the $4 coffee are needed and 5 pounds of the $3 coffee

are needed.

EVALUATION: Check the second equation.

4 xþ 3 y¼ 20 ð 3 : 75 Þ

4 ð 15 Þþ 3 ð 5 Þ¼ 75

60 þ 15 ¼ 75

75 ¼ 75

EXAMPLE:A person has $5000 to invest and decides to invest part of it at

4% and the rest of it at 6^12 %. If the total interest for the year is $245, how

much does the person have invested at each rate?

SOLUTION:

GOAL: You are being asked to find the amounts of money invested at each

rate.

STRATEGY: Letx¼the amount of money invested at 4%

andy¼the amount of money invested at 6

1

2

%

Since the total amount of money is $5000, the first equation is

xþy¼$ 5000

218 LESSON 18 Using Two Equations