Adding and Subtracting Decimals

Show your work for each problem.

1.
What is ?
1. a)4.8
2. b)3.7
3. c)3.8
4. d)2.8
Answer: 3.8
. Add tenths: . Add ones: . Result:
2.
Calculate
Answer: 3.3
. Tenths: . Ones: . Don't forget the decimal point!
3.
What is ?
1. a)7.29
2. b)7.39
3. c)8.39
4. d)7.49
Answer: 7.39
. Work from right to left: hundredths (), tenths (), ones ().
4.
Calculate
Answer: 9.9
. Tenths: . Ones: . Result:
5.
Calculate
Answer: 4.22
1. Subtract the hundredths: 2
2. Subtract the tenths: 2
3. Subtract the ones: 4
4. What is the final answer? 4.22
6.
What is ?
1. a)10.05
2. b)10.15
3. c)9.15
4. d)9.85
Answer: 10.15
. Hundredths: . Tenths: (write 1, carry 1). Ones: .
7.
Calculate
Answer: 4.45
. Borrowing is needed: hundredths, borrows to get tenths, ones.
8.
Calculate
Answer: 9.05
1. Add the hundredths: 15
2. Write 5 and carry 1 to tenths. Now add tenths: 10
3. Write 0 and carry 1 to ones. Now add ones: 9
4. What is the final answer? 9.05
9.
What is ?
1. a)4.72
2. b)5.32
3. c)5.72
4. d)4.82
Answer: 4.72
. Hundredths: (borrowed). Tenths: borrows to get . Ones: borrows to get .
10.
A notebook costs 3.49 dollars and a pen costs 1.75 dollars. What is the total cost?
Answer: 5.24
. Hundredths: (write 4, carry 1). Tenths: (write 2, carry 1). Ones: .
11.
Calculate
Answer: 5.45
1. For hundredths: requires borrowing. After borrowing from tenths, calculate 5
2. Tenths became . Borrow from ones. Now 4
3. Ones became 7. Calculate 5
4. What is the final answer? 5.45
12.
Calculate
Answer: 23.574
. Thousandths: . Hundredths: . Tenths: . Ones: (write 3, carry 1). Tens: .
13.
A runner's time improved from 54.28 seconds to 51.95 seconds. How much faster did they run?
1. a)3.33 seconds
2. b)2.23 seconds
3. c)2.33 seconds
4. d)2.43 seconds
Answer: 2.33 seconds
seconds. The improvement is the difference between the old (slower) time and the new (faster) time.
14.
Calculate
Answer: 6.33
1. Rewrite with decimal places. What is written as a decimal with two places? 20.00
2. For hundredths: requires borrowing. After borrowing, 3
3. For tenths (after giving 1 to hundredths): 3
4. For ones: (the 0 became 9 after borrowing) 6
5. For tens: 0
6. What is the final answer? 6.33
15.
You have 50 dollars. You spend 18.75 dollars on a book and 12.49 dollars on lunch. How much do you have left?
Answer: 18.76
1. First, find the total spent. Add . What is the sum? 31.24
2. Now subtract from 50. Write 50 as . Calculate 18.76