Printable math worksheet for practicing mental arithmetic with 40 addition, subtraction, multiplication, and division problems.

Let's solve each of these calculations step by step. These are all basic arithmetic problems involving addition, subtraction, multiplication, and division with decimals and whole numbers. I'll provide the answers along with brief explanations for clarity.

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Left Column (1–20)

1) 2 – 1.4
= 0.6
*Think: 2.0 – 1.4 = 0.6*

2) 4 × 0.3
= 1.2
*Think: 4 × 3 = 12, then place decimal: 1.2*

3) 0.5 + 0.9
= 1.4
*Think: 5 tenths + 9 tenths = 14 tenths = 1.4*

4) 240 ÷ 8
= 30
*Think: 8 × 30 = 240*

5) 3.1 – 0.6
= 2.5
*Think: 3.1 – 0.6 = 2.5*

6) 0.05 + 0.3
= 0.35
*Think: 5 hundredths + 30 hundredths = 35 hundredths = 0.35*

7) 1.28 × 10
= 12.8
*Moving decimal one place right: 1.28 → 12.8*

8) 8.2 ÷ 10
= 0.82
*Moving decimal one place left: 8.2 → 0.82*

9) 1 – 0.08
= 0.92
*Think: 1.00 – 0.08 = 0.92*

10) 30 × 90
= 2700
*Think: 3 × 9 = 27, add two zeros → 2700*

11) 0.6 + 4
= 4.6
*Add: 0.6 + 4.0 = 4.6*

12) 540 ÷ 60
= 9
*Think: 540 ÷ 60 = 54 ÷ 6 = 9*

13) 5 × 0.7
= 3.5
*5 × 7 = 35, so 3.5*

14) 0.15 + 0.6
= 0.75
*Think: 15 hundredths + 60 hundredths = 75 hundredths = 0.75*

15) 0.8 – 0.25
= 0.55
*Think: 0.80 – 0.25 = 0.55*

16) 0.61 × 100
= 61
*Move decimal two places right: 0.61 → 61*

17) 9 ÷ 10
= 0.9
*One-tenth of 9 is 0.9*

18) 0.2 + 0.9
= 1.1
*2 tenths + 9 tenths = 11 tenths = 1.1*

19) 4 – 1.9
= 2.1
*Think: 4.0 – 1.9 = 2.1*

20) 580 ÷ 100
= 5.8
*Move decimal two places left: 580 → 5.8*

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Right Column (21–40)

21) 6.5 + 2.8
= 9.3
*6 + 2 = 8, 0.5 + 0.8 = 1.3 → total 9.3*

22) 0.5 – 0.14
= 0.36
*Think: 0.50 – 0.14 = 0.36*

23) 4 × 0.9
= 3.6
*4 × 9 = 36 → 3.6*

24) 3.2 ÷ 4
= 0.8
*Think: 32 ÷ 4 = 8 → 3.2 ÷ 4 = 0.8*

25) 2.4 – 1.8
= 0.6
*2.4 – 1.8 = 0.6*

26) 1.7 ÷ 10
= 0.17
*Move decimal one place left: 1.7 → 0.17*

27) 0.07 + 0.25
= 0.32
*7 hundredths + 25 hundredths = 32 hundredths = 0.32*

28) 6.8 × 100
= 680
*Move decimal two places right: 6.8 → 680*

29) 8 ÷ 100
= 0.08
*Move decimal two places left: 8 → 0.08*

30) 9 – 2.6
= 6.4
*9.0 – 2.6 = 6.4*

31) 70 × 40
= 2800
*7 × 4 = 28, add two zeros → 2800*

32) 0.32 + 0.6
= 0.92
*32 hundredths + 60 hundredths = 92 hundredths = 0.92*

33) 420 ÷ 7
= 60
*7 × 60 = 420*

34) 6 × 0.5
= 3
*Half of 6 is 3*

35) 7.3 – 2.8
= 4.5
*7.3 – 2.8 = 4.5*

36) 0.28 + 0.15
= 0.43
*28 hundredths + 15 hundredths = 43 hundredths = 0.43*

37) 0.87 – 0.3
= 0.57
*0.87 – 0.30 = 0.57*

38) 8 × 0.7
= 5.6
*8 × 7 = 56 → 5.6*

39) 459 ÷ 100
= 4.59
*Move decimal two places left: 459 → 4.59*

40) 0.62 + 0.2
= 0.82
*62 hundredths + 20 hundredths = 82 hundredths = 0.82*

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✔ Final Answers:

| # | Answer |
|---|--------|
| 1) | 0.6 |
| 2) | 1.2 |
| 3) | 1.4 |
| 4) | 30 |
| 5) | 2.5 |
| 6) | 0.35 |
| 7) | 12.8 |
| 8) | 0.82 |
| 9) | 0.92 |
|10) | 2700 |
|11) | 4.6 |
|12) | 9 |
|13) | 3.5 |
|14) | 0.75 |
|15) | 0.55 |
|16) | 61 |
|17) | 0.9 |
|18) | 1.1 |
|19) | 2.1 |
|20) | 5.8 |
|21) | 9.3 |
|22) | 0.36 |
|23) | 3.6 |
|24) | 0.8 |
|25) | 0.6 |
|26) | 0.17 |
|27) | 0.32 |
|28) | 680 |
|29) | 0.08 |
|30) | 6.4 |
|31) | 2800 |
|32) | 0.92 |
|33) | 60 |
|34) | 3 |
|35) | 4.5 |
|36) | 0.43 |
|37) | 0.57 |
|38) | 5.6 |
|39) | 4.59 |
|40) | 0.82 |

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✔ All problems solved! This worksheet helps build mental math skills with decimals and operations. Practice like this improves number sense and fluency.