Mathematics Skills for Health Care Providers
Lesson 3 of 7
Subtraction of Whole Numbers
Learning Objectives
At the end of this lesson, you will be able to:
1. Understand and use the basic operation of subtraction of whole numbers.
2. Apply subtraction to your job.
Just as with addition, you will most likely use subtraction of whole numbers on a daily
basis. Subtraction is the opposite of addition. Therefore, if you can add, you can
subtract.
Vocabulary and Key Terms
borrow - When you cannot subtract a larger number from a smaller number, you must
borrow. Borrowing does not change the value of a number, but does enable you
to take a higher place value and add to a lower place value number.
difference - When you subtract, you take one number away from another to find the
difference.
minuend - The number being subtracted from is called the minuend. The minuend is
placed above the subtrahend.
subtrahend - The number being subtracted is called the subtrahend. The subtrahend
is placed below the minuend.
Unit 2 - Mathematics
Lesson 3
87
Prescription for Understanding
Subtracting and Borrowing:
1.
3,019 − 1,292 = ______________
Step 1.
3,019
− 1,292
Step 2.
3,019
− 1,292
7
Step 3.
Step 4.
2 9
2 9
3,019
− 1,292
27
3,019
− 1,292
1,727
Step 1. Put the larger number (3,019) on top. Line up the digits with units
under ones, tens under tens, hundreds over hundreds, etc.
Step 2. Starting with the ones (units) subtract. Since you cannot take 9 away
from 1, you must borrow.
Step 3. You cannot borrow from 0. Therefore, you must go one more place to
the left. Borrow 1 from the 3 to make 2 in the thousands place. Place 1
next to the 0 in the hundreds place to make 10.
Step 4. This still does not help the 1 in the tens place. Borrow again from the
10, put a 9 in the hundreds place, and place a 1 next to the 1 in the tens
place. Subtract.
Check Subtraction problem.
Original: 3,019 (minuend)
− 1,292 (subtrahend)
1,727 (difference)
Check:
1,292 (subtrahend)
+ 1,727 (difference)
3,019 (original minuend)
Add the answer (difference) to the number being subtracted (subtrahend). The
result should be the top number of the original problem (original minuend).
Unit 2 - Mathematics
Lesson 3
88
2.
There are two subtraction facts for every basic addition fact.
a. 9 + 6 = 15, you get these subtraction facts: 15 − 6 = 9 and 15 − 9 = 6.
b. 15 − 6 = 9 (difference)
ñ
minus sign means to subtract
ò
15 − 9 = 6 (difference)
3.
There are several ways to read subtractions:
a. 15 take away 9 is 6
b. 6 subtracted from 15 is 9
c. 15 minus 9 is 6
4.
Most single digit subtraction pairs you know, but you must be careful when you
have to borrow.
Examples:
Easy Problem
68
− 25
43
3
but
43
− 25
18
is a more difficult problem.
You borrow a 1 from 4 and
subtract 5 from 13, now you
subtract 2 from 3 to get 1.
Since we know these are the opposite of addition, both can easily be checked.
25
+ 43
68
Unit 2 - Mathematics
25
+ 18
43
Lesson 3
89
Examples
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
10 − 9 = 1
9−8=1
8−7=1
7−6=1
6−5=1
5−4=1
4−3=1
3−2=1
2−1=1
1−0=1
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
11 − 9 = 2
10 − 8 = 2
9−7=2
8−6=2
7−5=2
6−4=2
5−3=2
4−2=2
3−1=2
2−0=2
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
12 − 9 = 3
11 − 8 = 3
10 − 7 = 3
9−6=3
8−5=3
7−4=3
6−3=3
5−2=3
4−1=3
3−0=3
31.
32.
33.
34.
35.
36.
37.
38.
39.
40.
13 − 9 = 4
12 − 8 = 4
11 − 7 = 4
10 − 6 = 4
9−5=4
8−4=4
7−3=4
6−2=4
5−1=4
4−0=4
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
14 − 9 = 5
13 − 8 = 5
12 − 7 = 5
11 − 6 = 5
10 − 5 = 5
9−4=5
8−3=5
7−2=5
6−1=5
5−0=5
51.
52.
53.
54.
55.
56.
57.
58.
59.
60.
15 − 9 = 6
14 − 8 = 6
13 − 7 = 6
12 − 6 = 6
11 − 5 = 6
10 − 4 = 6
9−3=6
8−2=6
7−1=6
6−0=6
Unit 2 - Mathematics
Lesson 3
90
61.
62.
63.
64.
65.
66.
67.
68.
69.
70.
16 − 9 = 7
15 − 8 = 7
14 − 7 = 7
13 − 6 = 7
12 − 5 = 7
11 − 4 = 7
10 − 3 = 7
9−2=7
8−1=7
7−0=7
81.
82.
83.
84.
85.
86.
87.
88.
89.
90.
18 − 9 = 9
17 − 8 = 9
16 − 7 = 9
15 − 6 = 9
14 − 5 = 9
13 − 4 = 9
12 − 3 = 9
11 − 2 = 9
10 − 1 = 9
9−0=9
71.
72.
73.
74.
75.
76.
77.
78.
79.
80.
17 − 9 = 8
16 − 8 = 8
15 − 7 = 8
14 − 6 = 8
13 − 5 = 8
12 − 4 = 8
11 − 3 = 8
10 − 2 = 8
9−1=8
8−0=8
Note the difference in the following problems.
91.
14 − 5 = 9
92.
13 − 9 = 4
93.
9−6=3
94.
10 − 7 = 3
95.
7−3=4
96.
2−1=1
97.
8−4=4
98.
18 − 7 = 11
99.
18 − 3 = 15
100.
14 − 12 = 2
101.
11 − 4 = 7
102.
17 − 14 = 3
Unit 2 - Mathematics
Lesson 3
91
Skill Check
Now try these:
1.
79
− 53
2.
46
− 28
3.
135
− 69
4.
372
− 178
5.
1001
− 682
6.
2004
− 17
7.
3241
− 1610
8.
6748
− 748
9.
6974
− 28
10.
472
− 68
11.
798
− 41
12.
95
− 48
13.
48
− 29
14.
183
− 71
15.
35
− 17
16.
404
− 130
17.
696
− 595
18.
888
− 494
19.
921
− 129
20.
1840
− 697
21.
158
− 93
22.
44
− 20
23.
87
− 13
24.
98
− 41
25. 10,483
− 7,681
Now select your area of work and then turn to the appropriate page for “Let’s Apply to
Your Workplace” questions:
Nursing Assistant ---------------------- Page 93 - 94
Dietary Services ----------------------Page 95 - 96
Environmental Services --------------- Page 97 - 98
Unit 2 - Mathematics
Lesson 3
92
Let’s Apply to Nurse Assistant
Mathematics – Lesson 3 of 7
Nursing assistants use subtraction in many different ways. One example includes
determining the amount of supplies needed. Nursing assistants must check the supplies
and then decide whether to order more.
Example
There are thirty residents in C-wing that need lunches. Your food cart can hold only 15
trays at one time. How many trays remain to be delivered to the residents?
Total residents
Number trays on cart
30
− 15
15
There are 30 total residents. You have 15 food trays on the cart and 15 more to
deliver. You have 15 trays remaining to be delivered.
Unit 2 - Mathematics
Lesson 3
93
Exercise
1.
A resident requires three injections of insulin daily. There are 18 syringes for the
resident in the supply room. How many syringes are left at the end of the day?
a.
18
b.
14
c.
15
d.
17
2.
Mary Jane, who resides in D-wing, had a daily fluid intake of 320 cc’s. Her daily
output is 60 cc’s. What is the difference of the output to the intake?
a.
200
b.
210
c.
250
d.
260
3.
You are required to have 64 medium briefs on A-wing. You use 27 medium briefs
while making rounds. How many medium briefs remain in A-wing after rounds?
a.
37
b.
39
c.
27
d.
36
Unit 2 - Mathematics
Lesson 3
94
Let’s Apply to Dietary Services
Mathematics – Lesson 3 of 7
Dietary Services workers use subtraction of whole numbers in many different ways.
One example includes figuring how many pieces of a sheet cake remain after removing
some for serving.
Example
A sheet cake has forty-eight pieces. How many pieces will remain after 36 pieces are
served?
Total pieces of cake
Number of pieces served
48
− 36
12
Subtract 36 pieces served from the 48 total pieces. The remainder is 12.
Unit 2 - Mathematics
Lesson 3
95
Exercise
1.
Bill is serving orange juice to the residents. He has 96 glasses available. Bill
serves 87 residents. How many glasses does he have remaining?
a.
8
b.
9
c.
11
d.
7
2.
Judy uses 36 lbs. of bananas for breakfast. If her inventory held 67 lbs. before
the meal, how many lbs. of bananas does she still have in inventory?
a.
31
b.
37
c.
26
d.
39
3.
The total number of glasses needed per meal is 116. The total stock of glasses is
currently 300. How many glasses are available after a meal is served?
a.
192
b.
176
c.
184
d.
194
Unit 2 - Mathematics
Lesson 3
96
Let’s Apply to Environmental Services
Mathematics – Lesson 3 of 7
Environmental Services workers subtract whole numbers to inventory supplies and
linens, restock supplies, distribute briefs, distribute personal clothing to residents, etc.
When inventorying the linen closet, the worker must determine the total amount of
sheets in storage and then determine the amount needed.
Example
There are 30 residents in C-wing that need sheets. There are 18 sheets on hand in the
C-wing linen closet. How many sheets should be added to the C-wing linen closet?
Required:
On-hand:
Needed:
30
− 18
12
(30 − 18 = 12)
So the total number of sheets needed is 12.
Unit 2 - Mathematics
Lesson 3
97
Exercise
1.
An Environmental Services worker is stocking the residents’ brief cart. The worker
reviews the resident brief listing and verifies that he/she needs 60 small briefs to
fulfill the round. The cart contains 26 briefs. How many more briefs will he/she
need?
a.
38
b.
34
c.
39
d.
37
2.
Sue is stocking the residents’ brief supply unit. She reviews the resident brief
listing and verifies that she needs 125 small briefs. Sue has 250 briefs in storage.
How many briefs will she have left in storage after filling the cart?
a.
100
b.
125
c.
175
d.
150
3.
Jane is unloading a delivery cart. Jane reviews the packing slip and sees that
there are a total of 375 bed sheets being delivered. Jane will use 27 bed sheets
per day. How many sheets will be left in two days?
a.
206
b.
179
c.
321
d.
197
Unit 2 - Mathematics
Lesson 3
98