One hundred Honk Kong dollars
Decimals are the basis of currencies: there are 100 pennies in one pound.

Addition and Subtraction 2 (Difficult)

This is the second of our difficult quizzes on addition and subtraction. Like the previous quiz, it will give you a chance to practice adding and subtracting decimals. This may sound daunting at first, but it really is just the same as working with whole numbers – just make sure you know where to place that decimal point!

As you should be used to by now, when adding and subtracting any number, first work with the largest set of numbers (1,000s, 100s etc.), then the second largest (100s, 10s), then continue through the lower numbers (units, tenths, hundredths etc.).

It’s a good idea to have an estimate of the final answer – if nothing else, it will help you place the decimal point where it belongs!

1.
500 + 255.8 + 38.1 = ?
792.9
793.9
794.9
795.9
You could tackle this problem starting with the highest number: 500 + 255.8 + 38.1 = (500 + 255.8) + 38.1 = 755.8 + 38.1 = 793.9
2.
438.7 + 250.4 - 35.4 + 100 = ?
755.5
754.6
753.7
752.8
Breaking the problem into hundreds, tens, units and decimals helps: 438.7 + 250.4 - 35.4 + 100 = (400 + 200 + 100) + (30 + 50 - 30) + (8 - 5) + (0.7 + 0.4 - 0.4) = 700 + 50 + 3 + 0.7 = 753.7
3.
79.8 - 20.6 + 179.4 = ?
238.6
239.6
240.6
241.6
Splitting this into hundreds, tens, units and decimal will help: 79.8 - 20.6 + 179.4 = (100) + (70 + 70 - 20) + (9 + 9) + (0.8 + 0.4 - 0.6) = 100 + 120 + 18 + 0.6 = 238.6
4.
45.3 - 17.9 + 396.2 = ?
423.6
423.7
423.8
423.9
To avoid negative numbers, you can rearrange the problem: 45.3 - 17.9 + 396.2 = 396.2 + 45.3 - 17.9 = 441.5 - 17.9 = 423.6
5.
0.6 + 0.3 + 0.8 = ?
0.17
17
1.7
170
6 + 3 + 8 = 17, so 0.6 + 0.3 + 0.8 = 1.7. It's all about knowing where the decimal point should go!
6.
180.7 + 43.2 + 18.4 = ?
241.3
242.3
243.3
244.3
Hundreds first, then tens, units and, finally, decimals: 180.7 + 43.2 + 18.4 = (100) + (80 + 40 + 10) + (3 + 8) + (0.7 + 0.2 + 0.4) = 100 + 130 + 11 + 1.3 = 242.3
7.
837.1 - 342.5 = ?
494.3
494.4
494.5
494.6
You can treat this as a normal subtraction. Just make sure you put the decimal point in the right place. Making an estimate (the answer should be somewhere around 500) will help you avoid answers like 49.46 or 4,946!
8.
745.9 + 118.6 – 12.7 = ?
851.8
852.8
853.8
854.8
Hundreds, tens, units then decimals: 745.9 + 118.6 – 12.7 = (700 + 100) + (40 + 10 - 10) + (5 + 8 - 2) + (0.9 + 0.6 - 0.7) = 800 + 40 + 11 + 0.8 = 851.8
9.
12.7 + 15.3 + 112.2 = ?
140.1
140.2
140.3
140.4
Keep an eye out for decimals that add up to whole numbers: 12.7 + 15.3 is the same as 12 + 15 + 1
10.
7.7 - 16.9 - 6.6 + 111.3 = ?
95.2
95.3
95.4
95.5
Remeber, in multiple choice quizzes the final digit can give you the answer: 7 - 9 - 6 + 3 = -5, so you know that the last digit in the answer to 7.7 - 16.9 - 6.6 + 111.3 will also be a 5
Author:  Frank Evans

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