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See if you can do these tricky addition and subtraction problems.
Addition and Subtraction (Difficult)
Quiz about Adding and Subtracting Decimal Numbers
In this last section of 11-plus Maths quizzes on addition and subtraction, you are going to get some practice in adding and subtracting decimals.
Follow these tips to help you.
- Add the whole numbers first, then add the decimal parts. For example, 1.5 + 3.6 - 2.4 = (1 + 3 - 2) + (0.5 + 0.6 - 0.4) = 2 + 0.7 = 2.7
- With numbers less than 1,000, add the hundreds first, then the tens and then the ones. For example: 120 + 360 + 25 + 8 = (100 + 300) + (20 + 60 + 20) + (5 + 8) = 400 + 100 + 13 = 513
If you don't get 10 out of 10 the first time you play the quiz, don't worry. Try it again until you have a good grasp of this important aspect of Maths. Good luck!
1.
120.3 + 23.4 + 8.6 = ?
152.4
150.2
151.3
152.3
Add the whole numbers first, then add the decimal parts. 120.3 + 23.4 + 8.6 = (100) + (20 + 20) + (3 + 8) + (0.3 + 0.4 + 0.6) = 100 + 40 + 11 + 1.3 = 152.3
2.
69.9 - 40.6 + 123.4 = ?
152.8
152.6
152.7
152.5
69.9 - 40.6 + 123.4 = (100) + (60 + 20 - 40) + (9 + 3) + (0.9 + 0.4 - 0.6) = 100 + 40 + 12 + 0.7 = 152.7
3.
23.5 - 14.9 + 146.2 = ?
145.8
154.8
154.7
154.6
23.5 - 14.9 + 146.2 = (100) + (20 + 40 - 10) + (3 + 6 - 4) + (0.5 + 0.2 - 0.9) = 100 + 50 + 5 - 0.2 = 154.8
4.
8.8 - 6.4 - 8.8 + 19.6 = ?
13.2
31.2
13.1
13.0
8.8 - 6.4 - 8.8 + 19.6 = (10) + (9 - 6) + (0.6 - 0.4) = 10 + 3 + 0.2 = 13.2: don't waste time writing numbers that cancel each other out, e.g. 8.8 - 8.8 = 0
5.
2.3 + 5.6 + 12.3 = ?
19.1
20.1
20.2
20.3
Add the whole numbers first, then add the decimal parts. 2.3 + 5.6 + 12. 3 = (10) + (2 + 5 + 2) + (0.3 + 0.6 + 0.3) = 10 + 9 + 1.2 = 20.2
6.
345.9 + 38.6 - 17.2 = ?
367.3
376.3
367.4
365.3
345.9 + 38.6 - 17.2 = (300) + (40 + 30 - 10) + (5 + 8 - 7) + (0.9 + 0.6 - 0.2) = 300 + 60 + 6 + 1.3 = 367.3
7.
678.1 - 345.2 = ?
332.8
332.7
323.9
332.9
678.1 - 345.2 = (600 - 300) + (70 - 40) + (8 - 5) + (0.1 - 0.2) = 300 + 30 + 3 - 0.1 = 333 - 0.1 = 332.9: Note: with negative numbers, the negative sign is kept with each part of the number, e.g. - 678.6 is written as -600, -70, -8, and -0.6
8.
200 + 158.3 + 28.9 = ?
378.2
387.2
387.1
387.0
200 + 158.3 + 28.9 = (200 + 100) + (50 + 20) + (8 + 8) + (0.3 + 0.9) = 300 + 70 + 16 + 1.2 = 387.2
9.
0.8 + 0.2 + 0.7 = ?
1.5
1.2
0.7
1.7
0.8 + 0.2 + 0.7 = (0.8 + 0.2) + 0.7 = 1 + 0.7 = 1.7. Be on the LOOKOUT for decimals that sum to 1
10.
128.7 + 450.3 - 15.2 + 200 = ?
763.9
763.7
763.8
763.6
128.7 + 450.3 - 15.2 + 200 = (100 + 400 + 200) + (20 + 50 - 10) + (8 - 5) + (0.7 + 0.3 - 0.2) = 700 + 60 + 3 + 0.8 = 763.8
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