Math Word Problems Demystified - A Self Teaching Guide

7 
 7 þy¼ 15 
 7

y¼ 8

Hence, the number is 78.

EVALUATION: Check the information in the second equation.

Original number¼ 78

Reversed number¼ 87

Since 87 is 9 more than 78, the answer is correct.

EXAMPLE:A person has 8 coins consisting of quarters and dimes. If the

total amount of this change is $1.25, how many of each kind of coin are

there?

SOLUTION:

GOAL: You are being asked to find how many coins are quarters and how

many coins are dimes.

STRATEGY: Letx¼the number of quarters

y¼the number of dimes

25 x¼the value of the quarters

and 10y¼the value of the dimes

Since there are 8 coins, the first equation is

xþy¼ 8

Since the total values of the quarters plus the dimes is $1.25 or 125c, the

second equation is

25 xþ 10 y¼ 125

LESSON 18 Using Two Equations 211