Page 249 - Basic College Mathematics with Early Integers

226 C HAPTE R 3 I FRACTIONS

Objective Solving Problems by Adding or Subtracting
Unlike Fractions

Very often, real-world problems involve adding or subtracting unlike fractions.

PRACTICE 10 Example 10 Finding Total Weight
To repair her sidewalk, a 1 1 3
homeowner must pour cement in A freight truck has ton of computers, ton of televisions, and ton of small
8
3
4
three different locations. She appliances. Find the total weight of its load.
3 3
needs of a cubic yard, of a
5 10
1
cubic yard, and of a cubic
15 ~ ton a ton ≈ ton
yard for these locations. Find of of of
the total amount of cement the computers televisions appliances
homeowner needs.

Solution:

1. UNDERSTAND. Read and reread the problem. The phrase “total weight”
tells us to add.
2. TRANSLATE.
total weight of weight of weight of
In words: is plus plus
weight computers televisions appliances
T T T T T T T
total 1 1 3
Translate: = + +
weight 4 3 8
3. SOLVE: The LCD is 24.
1 1 3 1 6 1 8 3 3
+ + = # + # + #
4 3 8 4 6 3 8 8 3
6 8 9
= + +
24 24 24
23
=
24
4. INTERPRET. Check the solution. State your conclusion: The total weight of
23
the truck’s load is ton.
24
Work Practice 10

PRACTICE 11 Example 11 Calculating Flight Time
Find the difference in length 5
3 A flight from Tucson to Phoenix, Arizona, requires Arizona
Arizona
of two boards if one board is 12
4 1
2 of an hour. If the plane has been flying of an hour,
of a foot long and the other is 4
3 find how much time remains before landing. Phoenix Copyright 2012 Pearson Education, Inc.
of a foot long. 12 5 hour
Answers Tucson
29 1
10. cu yd 11. ft
30 12