You need to find the lowest common multiple when finding common denominators to add fractions. Highest common factors are also used in fraction or ratio calculations when you cancel down. This interactive worksheet will show you how to work them out.
Simon Singh has written a book about maths in the Simpsons. Read all about it here on the Guardian website.
Have a read of the article and find out about Fermat’s Last Theorem, Perfect Numbers, Narcissistic numbers, Mersenne Primes, Googols and Googolplexs and lots more! You may not need to know this stuff to pass your maths exam, but hopefully you’ll see that maths can be both fascinating and fun!
4+ 7 x 3
Do all the calculators give the same answer? What is the correct answer?
If you have a cheap four function calculator you will have got the answer 33, because it always calculates in the order you enter the sum. Unfortunately this is not mathematically correct!
If you used a scientific calculator you will have got the answer 25 which is correct. Scientific calculators understand the correct order to do calculations. Multiplication is more important than addition, so this comes first.
So how do we know what order to do calculations in? We use a rule called BIDMAS.
D ivision ÷
M ultiplication x
A ddition +
S ubtraction –
Always do brackets first. Then do any indices (like 2 squared or square root of 16). Some people refer to BODMAS where the O stands for “of”.) Division and multiplication come next (these have equal priority). Last is additions and subtractions (also equal priority)
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Learn how to count in English with the help of ESL instructor Megan Brach in these Howcast videos.
Have a go at this worksheet to find all the Prime Numbers less than 100.
Now try this much bigger Sieve to find all the Prime Numbers less than 400! Start by clicking on 2 and all the multiples of 2 will be removed. Then click on 3 to remove the multiples of 3 and continue clicking on the prime numbers until you are only left with red prime numbers.
Also take a look at this video