Multiplication trick: X by 25

26 05 2010

A neat trick to multiply any number by 25 in your head nice and quickly:

Multiplication trick

Credit goes to the mathchat blog!

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Divisibility tricks

2 05 2010

Is 6783043998 divisible by 3 without getting a remainder? Is it divisible by 7, 9 or 11? You don’t have to resort to the calculator to work this out, there are some great tricks for testing the divisibility of numbers.

Here’s the rules for checking divisibility by numbers between 1 and 10: Read the rest of this entry »

How to: expand brackets

25 04 2010

So you’re looking at the exam paper and you see a question that looks something like this:

Expand 3(2x + 5)

You’re thinking to yourself, ‘what do I do?’ and ‘what does expand mean?’ Read the rest of this entry »