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Mental Math: Adding & Subtracting — Easy Worksheet 2
Grade 3 · MathSheets Name: ____________________ Date: __________
Solve each problem in your head. Use the hint when there is one.
How to solve
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Example
350 + 200 = ___
Answer: 550
Not quite. The answer is
💡 Taking away 100 takes away 1 hundred, so only the hundreds digit goes down: 547 − 100 = 447.
✓ Correct!
Not quite. The answer is
💡 Taking away 100 takes away 1 hundred, so only the hundreds digit goes down: 547 − 100 = 447.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
301 + 100 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 80 is 8 tens. Count back by tens from 499: 489, 479, 469, 459, 449, 439, 429, 419. So 499 − 80 = 419.
✓ Correct!
Not quite. The answer is
💡 80 is 8 tens. Count back by tens from 499: 489, 479, 469, 459, 449, 439, 429, 419. So 499 − 80 = 419.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
771 - 100 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 Count up by tens from 20 to 100: that is 80. So 20 + 80 = 100.
✓ Correct!
Not quite. The answer is
💡 Count up by tens from 20 to 100: that is 80. So 20 + 80 = 100.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
128 + 400 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 Adding 300 adds 3 hundreds, so only the hundreds digit goes up: 693 + 300 = 993.
✓ Correct!
Not quite. The answer is
💡 Adding 300 adds 3 hundreds, so only the hundreds digit goes up: 693 + 300 = 993.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
811 - 200 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 80 is 8 tens. Count back by tens from 491: 481, 471, 461, 451, 441, 431, 421, 411. So 491 − 80 = 411.
✓ Correct!
Not quite. The answer is
💡 80 is 8 tens. Count back by tens from 491: 481, 471, 461, 451, 441, 431, 421, 411. So 491 − 80 = 411.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
877 - 400 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 197 is 3 less than 200. Add 200 first: 584 + 200 = 784. Then take away the extra 3: 784 − 3 = 781.
✓ Correct!
Not quite. The answer is
💡 197 is 3 less than 200. Add 200 first: 584 + 200 = 784. Then take away the extra 3: 784 − 3 = 781.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
684 + 200 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 Count up by tens from 50 to 100: that is 50. So 50 + 50 = 100.
✓ Correct!
Not quite. The answer is
💡 Count up by tens from 50 to 100: that is 50. So 50 + 50 = 100.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
574 - 300 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
Not quite. The answer is
💡 40 is 4 tens. Count back by tens from 763: 753, 743, 733, 723. So 763 − 40 = 723.
✓ Correct!
Not quite. The answer is
💡 40 is 4 tens. Count back by tens from 763: 753, 743, 733, 723. So 763 − 40 = 723.
💡 How to solve: Mental Math: Adding & Subtracting
Use friendly numbers. To add 200, just add 2 to the hundreds digit: 345 + 200 = 545. To add 298, add 300 and then take away 2: 145 + 300 = 445, and 445 - 2 = 443. To make the next hundred, count up: 370 + 30 = 400.
Try a similar one
788 - 100 = ___
✓ You've got it! Press Next to keep going. Not yet — the answer is . Read the steps above once more.
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Mental Math: Adding & Subtracting — Easy Worksheet 2
Solve each problem in your head. Use the hint when there is one.