MATHEMATICAL SHORTCUTS Maths may not be your thing but it is hard to avoid in For some games with numbers TIPS To calculate the total of a bill including tax add 1 before multiplying. Example 1 This also works in reverse – Example 2 In reverse – Thanks to KB for this one. What this is actually doing is acknowledging the original figure Anything ending in an “even” number is divisible by 2. Anything divisible by 9 is also divisible by 3. Thanks to KB for these. A quick way to do calculations is to drop the noughts at the ends Example – To add 120 + 90 add If you have to multiply a large number by 25, add two noughts to Example: 167 x When faced with a little poser like 27.5% of 50 for example, I Thanks for these Harvey Alexander When multiplying numbers ending in 5 by themselves e.g. 75 x 75 Deal with the left hand numbers first In this example the lefthand number is 7 Add 1 to this number i.e. 7 + 1 = 8 Multiply the original number 7 Now deal with the righthand numbers which are always 5 x 5 = 25 Therefore the answer is 5625 Here is another example – 35 x 35 3 + 1 = 4 4 x 3 = 12 5 x 5 = 25 Answer 1225 Thanks to Allan Brown for this contribution To make complex sums easier to handle, break down into simpler elements. Example: 6 x 348
A quick way to convert kilometres to miles is to drop the last digit and multiply by 6. Example: 72 kilometres = 7 x 6 = 42 miles
