Maths Quiz - Multiplication and Division 3 (Difficult) (Answers)
Welcome to this, the third quiz in our Difficult section of Eleven Plus maths quizzes on Multiplication and Division. In the first we learned about multiplying and dividing multiples of ten, like 100, 1,000 or 10,000. In the second we made things a little trickier and gave you some tips. In this quiz we shall help you learn how to do your calculations when dealing with decimals and large numbers.
If you have played our other quizzes, then this one shouldn’t be too hard – as long as you remember what you’ve learned! There are some simple ways to work out the answers, which you might not have thought of. Make sure you read all the helpful comments which follow the questions. They’ll make everything much easier to understand!
If you feel confident enough, put your calculators away and only use paper and pencil if you really must. Working out the answers in your head will hone your mind and sharpen your maths skills!
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To divide a number by 3,000 just divide the number by 3, then by 1,000.
Another option, as both numbers end with “000” is to ignore them and divide 96 by 3 – simple! |
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To multiply a number by 110: first multiply by 10, then multiply the original number by 100 and add the two answers together:
197.726 x 10 = 1,977.26 197.726 x 100 = 19,772.6 1,977.26 + 19,772.6 = 21,749.86 |
To divide a number by 200: just divide by 2, then divide by 100:
8,300 ÷ 200 = (8,300 ÷ 2) ÷ 100 = 4,150 ÷ 100 = 41.5 |
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To multiply a number by 95, first multiply the number by 100 and remember your answer. Next, times the original number by 10 and half it. Finally, subtract your second answer from your first:
68 x 95 = (68 x 100) - (68 x 10) ÷ 2 = 6,800 - (680 ÷ 2) = 6,800 - 340 = 6,460 |
To divide a number by 99, you can often just divide by 100 and repeat the number itself (ignoring any zeros):
46,000 ÷ 100 = 46 but 46,000 ÷ 99 = 464.64646464 etc…
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To multiply a number by 120, first multiply by 100 and remember your answer. Next, divide your answer by 5 and add this to your first answer:
83 x 120 = (83 x 100) + (83 x 100) ÷ 5 = 8,300 + (8,300 ÷ 5) = 8,300 + 1,660 = 9,960 |
To multiply by 10,000 simply move the digits 4 places to the left:
167.93628 x 10,000 = 1,679,362.8
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To divide by 10,000 simply move the digits 4 places to the right:
16,714 ÷ 10,000 = 1.6714 |
That was an easy one! Did you know, when asked to divide more difficult numbers by 15, you can use this trick - first divide by 10, then multiply by 2, and finally divide by 3:
75 ÷ 15 = ((75 ÷ 10) x 2) ÷ 3 = (7.5 x 2) ÷ 3 = 15 ÷ 3 = 5 |
27.83 x 5 = (27.83 x 10) ÷ 2 = 278.3 ÷ 2 = 139.15
27.83 x 100 = 2,783
2,783 + 139.15 = 2,922.15