Algebra Demystified 2nd Ed

256 algebra De mystif ieD

1488 4 540 2400

2028 4 2400

2028 2028

4 372

3

++=

+=

−−

=

=

x

x

x

x^772

4

x= 93

The student needs a 93 on her quiz to raise her average to 80.

Coin Problems

Coin problems are also common algebra applications. Usually the total number

of coins is given as well as the total dollar value. The question is normally “How

many of each coin is there?” When there is more than one coin involved, we let

x represent the number of one specific coin and the number of other coins in

terms of x. The steps involved are:

1. Let x represent the number of a specific coin.


2. Write the number of other coins in terms of x.


3. Multiply the value of the coin by its number; this gives the total amount
   of money represented by each coin.


4. Add all of the terms obtained in Step 3 and set equal to the total money
   value.


5. Solve for x.


6. Answer the question. Don’t forget this step! It is easy to feel like you are
   done when you’ve solved for x, but the answer to the question could be
   one step later.
   As in all word problems, units of measure must be consistent. In the follow-
   ing problems, this means that all money will need to be in terms of dollars or
   in terms of cents. We use dollars in the following examples.