Grade 3 Mental Math Worksheet with daily exercises for Monday through Thursday.

Let's solve each day's mental math problems step by step and explain the solutions.

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Monday

1. 19 + 19 =
→ 19 + 19 = 38
*Explanation:* Double 19: 20 + 20 = 40, minus 2 → 38.

2. 90 - 18 =
→ 90 - 18 = 72
*Explanation:* 90 - 10 = 80, then 80 - 8 = 72.

3. 9 × 4 =
→ 9 × 4 = 36
*Explanation:* 9×4 is a basic multiplication fact.

4. What’s halfway between 70 & 80?
→ (70 + 80) ÷ 2 = 150 ÷ 2 = 75
*Explanation:* Average of two numbers.

5. Value of the 8 in 861?
→ The 8 is in the hundreds place → 800
*Explanation:* 8 × 100 = 800.

6. How many sides does a square have?
→ 4 sides
*Explanation:* A square has 4 equal sides.

7. Write =, > or < : 112 ___ 110
→ 112 > 110
*Explanation:* 112 is greater than 110.

8. 80 + ___ = 210
→ 210 - 80 = 130
*Explanation:* Subtract 80 from 210 to find the missing number.

9. 9.2 + 0.3 =
→ 9.5
*Explanation:* Add decimals: 9.2 + 0.3 = 9.5

10. How many 6s make 24?
→ 24 ÷ 6 = 4
*Explanation:* 6 × 4 = 24.

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Tuesday

1. 36 + 35 =
→ 36 + 35 = 71
*Explanation:* 30+30=60, 6+5=11, 60+11=71.

2. 135 - 95 =
→ 135 - 95 = 40
*Explanation:* 135 - 100 = 35, but we subtracted 5 too many, so add back 5 → 35 + 5 = 40.

3. 8 × 3 =
→ 24
*Explanation:* Basic multiplication.

4. What’s halfway between 60 & 100?
→ (60 + 100) ÷ 2 = 160 ÷ 2 = 80
*Explanation:* Average of two numbers.

5. Value of the 2 in 682?
→ 2 is in the ones place → 2
*Explanation:* 2 × 1 = 2.

6. How many sides does a pentagon have?
→ 5 sides
*Explanation:* Pentagon = 5 sides.

7. Write =, > or < : 91 ___ 91
→ 91 = 91
*Explanation:* Same number → equal.

8. 57 + ___ = 117
→ 117 - 57 = 60
*Explanation:* Subtract 57 from 117.

9. 8.5 + 1.5 =
→ 10.0
*Explanation:* 8.5 + 1.5 = 10.0

10. How many 3s make 27?
→ 27 ÷ 3 = 9
*Explanation:* 3 × 9 = 27.

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Wednesday

1. 115 + 90 =
→ 115 + 90 = 205
*Explanation:* 115 + 90 = 205 (or 100 + 90 = 190, plus 15 = 205).

2. 62 - 31 =
→ 62 - 31 = 31
*Explanation:* 62 - 30 = 32, minus 1 more → 31.

3. 12 × 2 =
→ 24
*Explanation:* Double 12.

4. What’s halfway between 12 & 24?
→ (12 + 24) ÷ 2 = 36 ÷ 2 = 18
*Explanation:* Average.

5. Value of the 3 in 3975?
→ 3 is in the thousands place → 3000
*Explanation:* 3 × 1000 = 3000.

6. How many sides does an oval have?
→ 0 (or none)
*Explanation:* An oval is a curved shape with no straight sides.

7. Write =, > or < : 52 ___ 25
→ 52 > 25
*Explanation:* 52 is greater than 25.

8. 250 + ___ = 600
→ 600 - 250 = 350
*Explanation:* Subtract 250 from 600.

9. 3.6 + 0.4 =
→ 4.0
*Explanation:* 3.6 + 0.4 = 4.0

10. How many 5s make 40?
→ 40 ÷ 5 = 8
*Explanation:* 5 × 8 = 40.

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Thursday

1. 44 + 25 =
→ 44 + 25 = 69
*Explanation:* 40 + 20 = 60, 4 + 5 = 9 → 69.

2. 54 - 18 =
→ 54 - 18 = 36
*Explanation:* 54 - 10 = 44, 44 - 8 = 36.

3. 7 × 5 =
→ 35
*Explanation:* Basic multiplication.

4. What’s halfway between 24 & 30?
→ (24 + 30) ÷ 2 = 54 ÷ 2 = 27
*Explanation:* Average.

5. Value of the 9 in 5941?
→ 9 is in the hundreds place → 900
*Explanation:* 9 × 100 = 900.

6. How many sides does a triangle have?
→ 3 sides
*Explanation:* Triangle = 3 sides.

7. Write =, > or < : 17 ___ 71
→ 17 < 71
*Explanation:* 17 is less than 71.

8. 14 + ___ = 28
→ 28 - 14 = 14
*Explanation:* Subtract 14 from 28.

9. 2.5 + 2.5 =
→ 5.0
*Explanation:* 2.5 + 2.5 = 5.0

10. How many 10s make 60?
→ 60 ÷ 10 = 6
*Explanation:* 10 × 6 = 60.

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✔ Final Answers:

#### Monday
1. 38
2. 72
3. 36
4. 75
5. 800
6. 4
7. >
8. 130
9. 9.5
10. 4

#### Tuesday
1. 71
2. 40
3. 24
4. 80
5. 2
6. 5
7. =
8. 60
9. 10.0
10. 9

#### Wednesday
1. 205
2. 31
3. 24
4. 18
5. 3000
6. 0
7. >
8. 350
9. 4.0
10. 8

#### Thursday
1. 69
2. 36
3. 35
4. 27
5. 900
6. 3
7. <
8. 14
9. 5.0
10. 6

Let me know if you'd like this formatted as a printable answer key!