MATHS TRICKS -II

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Adding Time
Here is a nice simple way to add hours and minutes together:

Let's add 1 hr and 35 mins and 3 hr 55 mins together.


What you do is this:
make the 1 hr 35 mins into one number, which will give us 135 and do the same for the other number 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 mins 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 mins!

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?

Well 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


So 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

What you do is this:

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.




Lets try 4 into 3436546
So, from our example, take the last number, 6 and add it to twice 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.
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