Top 10 Maths tricks Every Student

Should See

–

1. The 11 Times Trick

We all know the trick when multiplying

by ten – add 0 to the end of the

number, but did you know there is an

equally easy trick for multiplying a two

digit number by 11? This is it:

Take the original number and imagine a

space between the two digits (in this

example we will use 52:

5_2

Now add the two numbers together and

put them in the middle:

5_(5+2)_2

That is it – you have the answer: 572. If

the numbers in the middle add up to a

2 digit number, just insert the second

number and add 1 to the first:

9_(9+9)_9

(9+1)_8_9

10_8_9

1089 – It works every time.

–

2. Quick Square

If you need to square a 2 digit number

ending in 5, you can do so very easily

with this trick. Mulitply the first digit by

itself + 1, and put 25 on the end. That is

all!

25 = (2x(2+1)) & 25

2 x 3 = 6

625

–

3. Multiply by 5

Most people memorize the 5 times

tables very easily, but when you get in

to larger numbers it gets more complex

– or does it? This trick is super easy.

Take any number, then divide it by 2 (in

other words, halve the number). If the

result is whole, add a 0 at the end. If it

is not, ignore the remainder and add a

5 at the end. It works everytime:

2682 x 5 = (2682 / 2) & 5 or 0

2682 / 2 = 1341 (whole number so add

0)

13410

Let’s try another:

5887 x 5

2943.5 (fractional number (ignore

remainder, add 5)

29435

–

4. Multiply by 9

This one is simple – to multiple any

number between 1 and 9 by 9 hold

both hands in front of your face – drop

the finger that corresponds to the

number you are multiplying (for

example 9×3 – drop

your third finger) – count the fingers

before the dropped finger (in the case

of 9×3 it is 2) then count the numbers

after (in this case 7) – the answer is 27.

–

5. Multiply by 4

This is a very simple trick which may

appear obvious to some, but to others it

is not. The trick is to simply multiply by

two, then multiply by two again:

58 x 4 = (58 x 2) + (58 x 2) = (116) +

(116) = 232

–

6. Calculate a Tip

If you need to leave a 15% tip, here is

the easy way to do it. Work out 10%

(divide the number by 10) – then add

that number to half its value and you

have

your answer:

15% of $25 = (10% of 25) + ((10% of

25) / 2)

$2.50 + $1.25 = $3.75

–

7. Tough Multiplication

If you have a large number to multiply

and one of the numbers is even, you

can easily subdivide to get to the

answer:

32 x 125, is the same as:

16 x 250 is the same as:

8 x 500 is the same as:

4 x 1000 = 4,000

–

8. Dividing by 5

Dividing a large number by five is

actually very simple. All you do is

multiply by 2 and move the

decimal point:

195 / 5

Step1: 195 * 2 = 390

Step2: Move the decimal: 39.0 or just

39

2978 / 5

step 1: 2978 * 2 = 5956

Step2: 595.6

–

9. Subtracting from 1,000

To subtract a large number from 1,000

you can use this basic rule: subtract all

but the last number from 9, then

subtract the last number from 10:

1000

-648

step1: subtract 6 from 9 = 3

step2: subtract 4 from 9 = 5

step3: subtract 8 from 10 = 2

answer: 352

–

10. Assorted Multiplication Rules

Multiply by 5: Multiply by 10 and divide

by 2.

Multiply by 6: Sometimes multiplying

by 3 and then 2 is easy.

Multiply by 9: Multiply by 10 and

subtract the original number.

Multiply by 12: Multiply by 10 and add

twice the original number.

Multiply by 13: Multiply by 3 and add

10 times original number.

Multiply by 14: Multiply by 7 and then

multiply by 2

Multiply by 15: Multiply by 10 and add

5 times the original number, as above.

Multiply by 16: You can double four

times, if you want to. Or you can

multiply by 8 and then by 2.

Multiply by 17: Multiply by 7 and add

10 times original number.

Multiply by 18: Multiply by 20 and

subtract twice the original number

(which is obvious from the first step).

Multiply by 19: Multiply by 20 and

subtract the original number.

Multiply by 24: Multiply by 8 and then

multiply by 3.

Multiply by 27: Multiply by 30 and

subtract 3 times the original number

(which is obvious from the first step).

Multiply by 45: Multiply by 50 and

subtract 5 times the original number

(which is obvious from the first step).

Multiply by 90: Multiply by 9 (as above)

and put a zero on the right.

Multiply by 98: Multiply by 100 and

subtract twice the original number.

Multiply by 99: Multiply by 100 and

subtract the original number.

–

If only some of us had gotten this tricks

while in secondary school, who

knows……….we all could have had A1

mathematics in waec.

Credit:Nairaland

## Top 10 Maths Tricks Every Student Should See

14
Jan

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