Question

round each decimal to the nearest ten. then add or subtract.

1. 23.78 + 10.45 =
2. 83.69 − 55.41 =

12.
37.58
−21.25
13.
32.56
+ 6.7
14.
25.21
−12.47

Explanation:

Step1: Round 23.78 to nearest ten

23.78 rounded to nearest ten: look at ones digit (3) < 5, so round down to 20.

Step2: Round 10.45 to nearest ten

10.45: ones digit 0, so round to 10.

Step3: Add the rounded numbers

20 + 10 = 30.

Step1 (Q11): Round 83.69 to nearest ten

83.69: ones digit 3 < 5, round to 80.

Step2 (Q11): Round 55.41 to nearest ten

55.41: ones digit 5, round up to 60.

Step3 (Q11): Subtract rounded numbers

80 - 60 = 20.

Step1 (Q12): Round 37.58 to nearest ten

37.58: ones digit 7 ≥ 5, round to 40.

Step2 (Q12): Round 21.25 to nearest ten

21.25: ones digit 1 < 5, round to 20.

Step3 (Q12): Subtract rounded numbers

40 - 20 = 20.

Step1 (Q13): Round 32.56 to nearest ten

32.56: ones digit 2 < 5, round to 30.

Step2 (Q13): Round 6.7 to nearest ten

6.7: ones digit 6 ≥ 5, round to 10.

Step3 (Q13): Add rounded numbers

30 + 10 = 40.

Step1 (Q14): Round 25.21 to nearest ten

25.21: ones digit 5, round up to 30.

Step2 (Q14): Round 12.47 to nearest ten

12.47: ones digit 2 < 5, round to 10.

Step3 (Q14): Subtract rounded numbers

30 - 10 = 20.

Answer:

1. 30
2. 20
3. 20
4. 40
5. 20