Printable mental math worksheet featuring basic arithmetic problems and number sense questions for practice.

Let’s go step by step through each problem in the worksheet. I’ll solve them one at a time, check my work, and then give you the final answers clearly.

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1. 12 more than 500

→ 500 + 12 = 512

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**Make 120:
10 + ___ → 120 - 10 = 110
20 + ___ → 120 - 20 = 100

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The number that comes before 711

→ That’s 711 - 1 = 710

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**Start with 10
Add 4 → 10 + 4 = 14
Subtract 2 → 14 - 2 = 12
Add 1 → 12 + 1 = 13

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3 less than 902

→ 902 - 3 = 899

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**Count by 5’s:
5, 10, 15, ___ → next is 20 (already given)
Then 20, 25, 30, ___ → next is 35

Wait — let me read again:

It says:
> Count by "5"s, what comes next?
> 5, 10, 15, ____
> 20, 25, 30, ____

So first blank after 15 → 20
Second blank after 30 → 35

But note: 20 is already written below, so maybe they want the *next* after 30? Yes — it's 35

Actually, looking at layout:

First line: 5, 10, 15, ___ → answer: 20
Second line: 20, 25, 30, ___ → answer: 35

Yes.

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11 less than 111

→ 111 - 11 = 100

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If 10 + 20 is 30, What is 100 + 200?

→ Same pattern: 100 + 200 = 300

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Which is more: 202 or 212?

→ 212 > 202 → Answer: 212

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What is -203 + 7?

→ Think: Start at -203, add 7 → move right on number line.

-203 + 7 = -196

(Check: 203 - 7 = 196, so negative side: -196)

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Which is less: 880 or 801?

→ 801 < 880 → Answer: 801

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A number between 500 and 510. It has 5 in its ones place.

Numbers between 500 and 510: 501, 502, ..., 509

Which has 5 in ones place? → Only 505

(Ones digit is last digit → 505 ends in 5)

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What is 43 + 43?

→ 40 + 40 = 80
3 + 3 = 6
Total: 80 + 6 = 86

Or: 43 × 2 = 86

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6 plus what number equals 11?

→ 11 - 6 = 5

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20 + 25 = ?

→ 20 + 25 = 45

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Is 15 odd or even?

→ Odd numbers end in 1, 3, 5, 7, 9 → 15 ends in 5 → odd

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Now, compiling all answers in order as they appear in the table (left column first, then right column for each row):

Row 1 Left: 12 more than 500 → 512
Row 1 Right: Make 120 → 10 + 110, 20 + 100

Row 2 Left: Before 711 → 710
Row 2 Right: Start with 10 → Add 4 → 14, subtract 2 → 12, add 1 → 13

Row 3 Left: 3 less than 902 → 899
Row 3 Right: Count by 5s → after 15: 20, after 30: 35

Row 4 Left: 11 less than 111 → 100
Row 4 Right: 100 + 200 → 300

Row 5 Left: Which is more? → 212
Row 5 Right: -203 + 7 → -196

Row 6 Left: Which is less? → 801
Row 6 Right: Number between 500–510 with 5 in ones → 505

Row 7 Left: 43 + 43 → 86
Row 7 Right: 6 + ? = 11 → 5

Row 8 Left: 20 + 25 → 45
Row 8 Right: Is 15 odd or even? → odd

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Final Answer:

512
110, 100
710
14, 12, 13
899
20, 35
100
300
212
-196
801
505
86
5
45
odd