Contents |
1. |
Multiplying By 11 |
2. |
Is it divisible By 4? |
3. |
Multiplying By 12 Shortcut |
4. |
Converting Kilos to Pounds |
5. |
Adding Time |
6. |
Converting Celsius to Fahrenheit |
7. |
5 Squared Shortcut |
8. |
Decimal Equivalents of Fractions |
9. |
Kilometres to Miles |
Multiplying by 11 shortcut |
This technique teaches you how to multiply any number by eleven, easily and quickly. |
We will take a few examples and from these you will see the pattern used and also how |
easy they are to do. |
So, to begin let’s try 12 time 11. |
First things first you will ignore the 11 for the moment and concentrate on the 12. |
Split the twelve apart, like so: |
12 |
Add these two digits together 1 + 2 = 3 |
1+2 = 3 |
Place the answer, 3 in between the 12 to give 132 |
11 X 12 = |
132 |
Let’s try another: |
48 X 11 |
again, leave the 11 alone for a moment and work with the 48 |
4 + 8 = 12 |
So now we have to put the 12 in between the 4 and 8 but |
don’t |
do this: |
4128 as that is |
wrong |
... |
First, do this: Place the 2 from the twelve in between the 4 and 8 giving 428. |
Now we need to input the 1 from the twelve into our answer also, and to do this just add |
the one from 12 to the 4 of 428 giving 528! |
Ok, one more |
74 X 11 |
7+4 = 11 |
7 (put the 1 from the right of 11 in) and 4 |
then add the 1 from the left of 11 to the 7 |
74 X 11 = 814 |
This is a really simple method and will save you so much time with your 11 times tables. |
Is it divisible by four? |
This little math trick will show you whether a number is divisible by four or not. |
So, this is how it works. |
Let's look at 1234 |
Does 4 divide evenly into 1234? |
For 4 to divide into any number we have to make sure that the last number is even |
. |
If it is an odd number, there is no way it will go in evenly. |
So, for example, 4 will not go evenly into 1233 or 1235 |
now we know that for 4 to divide evenly into any number the number has to end with an |
even number. |
Back to the question... |
4 into 1234, the solution: |
Take the last number and add it to 2 times the second last number |
. If 4 goes evenly |
into this number then you know that 4 will go evenly into the whole number. |
So |
4 + (2 X 3) = 10 |
4 goes into 10 two times with a remainder of 2 so it does not go in evenly. |
Therefore 4 into 1234 does not go in completely. |
Let’s try 4 into 3436546 |
So, from our example, take the last number, 6 and add it to two times the penultimate |
number, 4 |
6 + (2 X 4) = 14 |
4 goes into 14 three times with two remainder. |
So it doesn't go in evenly. |
Let's try one more. |
4 into 212334436 |
6 + (2 X 3) = 12 |
4 goes into 12 three times with 0 remainder. |
Therefore 4 goes into 234436 evenly. |
So what use is this trick to you? |
Well if you have learnt the tutorial at Memorymentor.com about telling the day in any |
year, then you can use it in working out whether the year you are calculating is a leap |
year or not. |
Multiplying by 12 shortcut |
So how does the 12's shortcut work? |
Let's take a look. |
12 X 7 |
the first thing is to always multiply the 1 of the twelve by the number we are multiplying |
by, in this case 7. So 1 X 7 = 7. |
Multiply this 7 by 10 giving 70. (Why? We are working with BASES here. Bases are the |
fundamentals to easy calculations for all multiplication tables. To find out more check out |
our Vedic Maths ebook at |
http://www.memorymentor.com/big_brain.htm |
) |
Now multiply the 7 by the 2 of twelve giving 14. Add this to 70 giving 84. |
Therefore 7 X 12 = 84 |
Let's try another: |
17 X 12 |
Remember, multiply the 17 by the 1 in 12 and multiply by 10 |
( |
Just add a zero to the end |
): |
1 X 17 = 17, multiplied by 10 giving 170. |
Multiply 17 by 2 giving 34. |
Add 34 to 170 giving 204. |
So 17 X 12 = 204 |
lets go one more |
24 X 12 |
Multiply 24 X 1 = 24. Multiply by 10 giving 240. |
Multiply 24 by 2 = 48. Add to 240 giving us 288 |
24 X 12 = 288 (these are Seriously Simple Sums to do aren’t they?!) |
Converting Kilos to pounds |
In this section you will learn how to convert Kilos to Pounds, and Vice Versa. |
Let’s start off with looking at converting Kilos to pounds. 86 kilos into pounds: |
Step one, multiply the kilos by TWO. |
To do this, just double the kilos. |
86 x 2 = 172 |
Step two, divide the answer by ten. |
To do this, just put a decimal point one place in from the right. |
172 / 10 = 17.2 |
Step three, add step two’s answer to step one’s answer. |
172 + 17.2 = 189.2 |
86 Kilos = 189.2 pounds |
Let’s try: |
50 Kilos to pounds: |
Step one, multiply the kilos by TWO. |
To do this, just double the kilos. |
50 x 2 = 100 |
Step two, divide the answer by ten. |
To do this, just put a decimal point one place in from the right. |
100 / 10 = 10 |
Step three, add step two’s answer to step one’s answer. |
100 + 10 = 110 |
50 Kilos = 110 pounds |
Adding Time |
Here is a nice simple way to add hours and minutes together: |
Let's add 1 hr and 35 minutes and 3 hr 55 minutes together. |
What you do is this: |
make the 1 hr 35 minutes into one number, which will give us 135 and do the same for |
the other number, 3 hours 55 minutes, giving us 355 |
Now you want to add these two numbers together: |
135 |
355 |
____ |
490 |
So we now have a sub total of 490. |
What you need to do to this and all sub totals is |
add the time constant of 40 |
. |
No matter what the hours and minutes are, just add the 40 time constant to the sub |
total. |
490 + 40 = 530 |
so we can now see our answer is 5 hrs and 30 minutes! |
Temperature Conversions |
This is a shortcut to convert Fahrenheit to Celsius and vice versa. |
The answer you will get will not be an exact one, but it will give you an idea of the |
temperature you are looking at. |
Fahrenheit to Celsius: |
Take 30 away from the Fahrenheit, and then divide the answer by two. This is your |
answer in Celsius. |
Example: |
74 Fahrenheit - 30 = 44. Then divide by two, 22 Celsius. |
So 74 Fahrenheit = 22 Celsius. |
Celsius to Fahrenheit just do the reverse: |
Double it, and then add 30. |
30 Celsius double it, is 60, then add 30 is 90 |
30 Celsius = 90 Fahrenheit |
Remember, the answer is not exact but it gives you a rough idea. |
5 Squared Shortcut |
Here is a really quick way to square any number with a 5 on the end. |
Let’s take |
Ok, so what you have to do is split up the numbers, giving you |
And |
Forget about the for the moment and do this: |
Always add 1, adding 1 to the 4, so we get 4 + 1 = 5 |
Then multiply this answer, 5, by the original first number, 4 |
5 X 4 = 20 |
So what you have is 20 and |
Everyone knows = 25 right? Well it does. This is what makes it easy. |
Put the two answers together and that's the answer! |
2025 |
This works for any number ending in but when the numbers get over 100 it tends to get |
a little trickier with the multiplication. |
Give it a try with another number. |
Try , it isn't difficult. |
Split the numbers apart: |
8 and |
Again, forget about the |
Add 1 to 8 |
8 + 1 = 9 |
Multiply 9 by the first number, which was 8 |
9 X 8 =72 |
Now, put all the numbers together, 72 and |
= 25 |
So the answer is 7225 |
Try it out in a calculator once you have done it. |
Decimals Equivalents of Fractions |
With a little practice, it's not hard to recall the decimal equivalents of fractions up to |
10/11! |
First, there are 3 you should know already: |
1/2 = .5 |
1/3 = .333... |
1/4 = .25 |
Starting with the thirds, of which you already know one: |
1/3 = .333... |
2/3 = .666... |
You also know 2 of the 4ths, as well, so there's only one new one to learn: |
1/4 = .25 |
2/4 = 1/2 = .5 |
3/4 = .75 |
Fifths are very easy. Take the numerator (the number on top), double it, and stick a |
decimal in front of it. |
1/5 = .2 |
2/5 = .4 |
3/5 = .6 |
4/5 = .8 |
There are only two new decimal equivalents to learn with the 6ths: |
1/6 = .1666... |
2/6 = 1/3 = .333... |
3/6 = 1/2 = .5 |
4/6 = 2/3 = .666... |
5/6 = .8333... |
What about 7ths? We'll come back to them at the end. They're very unique. |
8ths aren't that hard to learn, as they're just smaller steps than 4ths. If you have trouble |
with any of the 8ths, find the nearest 4th, and add .125 if needed: |
1/8 = .125 |
2/8 = 1/4 = .25 |
3/8 = .375 |
4/8 = 1/2 = .5 |
5/8 = .625 |
6/8 = 3/4 = .75 |
7/8 = .875 |
9ths are almost too easy: |
1/9 = .111... |
2/9 = .222... |
3/9 = .333... |
4/9 = .444... |
5/9 = .555... |
6/9 = .666... |
7/9 = .777... |
8/9 = .888... |
10ths are very easy, as well. Just put a decimal in front of the numerator: |
1/10 = .1 |
2/10 = .2 |
3/10 = .3 |
4/10 = .4 |
5/10 = .5 |
6/10 = .6 |
7/10 = .7 |
8/10 = .8 |
9/10 = .9 |
Remember how easy 9ths were? 11th are easy in a similar way, assuming you know your |
multiples of 9: |
1/11 = .090909... |
2/11 = .181818... |
3/11 = .272727... |
4/11 = .363636... |
5/11 = .454545... |
6/11 = .545454... |
7/11 = .636363... |
8/11 = .727272... |
9/11 = .818181... |
10/11 = .909090... |
As long as you can remember the pattern for each fraction, it is quite simple to work out |
the decimal place as far as you want or need to go! |
Oh, I almost forgot! We haven't done 7ths yet, have we? |
One-seventh is an interesting number: |
1/7 = .142857142857142857... |
For now, just think of one-seventh as: .142857 |
See if you notice any pattern in the 7ths: |
1/7 = .142857... |
2/7 = .285714... |
3/7 = .428571... |
4/7 = .571428... |
5/7 = .714285... |
6/7 = .857142... |
Notice that the 6 digits in the 7ths ALWAYS stay in the same order and the starting digit |
is the only thing that changes! |
If you know your multiples of 14 up to 6, it isn't difficult to work out where to begin the |
decimal number. Look at this: |
For 1/7, think "1 * 14", giving us .14 as the starting point. |
For 2/7, think "2 * 14", giving us .28 as the starting point. |
For 3/7, think "3 * 14", giving us .42 as the starting point. |
For 4/14, 5/14 and 6/14, you'll have to adjust upward by 1: |
For 4/7, think "(4 * 14) + 1", giving us .57 as the starting point. |
For 5/7, think "(5 * 14) + 1", giving us .71 as the starting point. |
For 6/7, think "(6 * 14) + 1", giving us .85 as the starting point. |
Practice these, and you'll have the decimal equivalents of everything from 1/2 to 10/11 at |
your finger tips! |
If you want to demonstrate this skill to other people, and you know your multiplication |
tables up to the hundreds for each number 1-9, then give them a calculator and ask for a |
2-digit number (3-digit number, if you're up to it!) to be divided by a 1-digit number. |
If they give you 96 divided by 7, for example, you can think, "Hmm... the closest |
multiple of 7 is 91, which is 13 * 7, with 5 left over. So the answer is 13 and 5/7, or: |
13.7142857!" |
Converting Kilometres to Miles |
This is a useful method for when travelling between imperial and metric countries and |
need to know what kilometres to miles are. |
The formula to convert kilometres to miles is number of (kilometres / 8 ) X 5 |
So lets try 80 kilometres into miles |
80/8 = 10 |
multiplied by 5 is 50 miles! |
Another example |
40 kilometres |
40 / 8 = 5 |
5 X 5= 25 miles |