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Top 10 Maths Tricks Every Student Should See

14 Jan

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

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Posted by on January 14, 2017 in Uncategorized

 

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