Some speed maths stuff

The approach would be to get the denominator to either a 100 or a 1000 because that is what percentages is all bout.
Simply focus on the fact that how do the given denominators reach 100/1000. I have left some blank because they are very obvious.

The following are the stations between 100 and 1000

100
111 - Reduce 10%
125 - Multiply by 8
133 - Reduce 1/4
150 - Reduce 1/3
166 - Multiply by 6
182 - Add 10%
200
222 - Reduce 10%
250
273 - Add 10%
300
333 - Reduce 10%
364
400
455 - Add 10%
500
555 - Reduce 10%
600
666 - Add Half
700
750 - Add 1/3
800
833 - Add 20%
875 - Add 1/7
900
910 - Add 9%
950 - Add 5%
1000

So Task (1) you have to mug up the values of these stations. It is very important that these values are memorized because this will help you in
knowing which number to reach from any given number. e.g. if the denominator is 887 you know you have to reach for 900 or 875 and so on.

Task (2) Practice!

Below is an approach to tackle (three digit /three digit) with consummate ease. We shall attempt to understand it with examples.

Example 1:
What is 145/182 ------------------79.5

Steps
1. add 10% to numerator and denominator...
2. it becomes 159/200 ...............which is 79.5
( the answer from the calculator is 79.6)

Example 2:
123/178....???

Step1:- which station is closest to it?.............................200?...or some say 150. Either is good. (identification took 2 seconds)

Step 2:- what do I have to do to go from 178 to 200/150..................add 22/subtract 28... (another 2 seconds.)

Step 3:- so if I add 22................i am actually adding slightly less than 13% of 178 to itself.

This part is tricky.. here is how I got it:

This is how u need to think---
Our number is 178. Thus, 10% of it is 17.8
22 definitely more than 10% .
if 10% = 17.8 then 5% = 8.xx

And 2.5% = 4.xxx (don't even bother to calculate xxx)
which means its around 12.5........or 13 or 12..........

Add same to numerator...........10% of 123 = 12.3
1% = 1.23 so 2% = 2.46

So 12% = 15?
So it becomes 138/200 = 69%?
(calculator answer is 69.1).

All you require to calculate is what is 10% 1%...and approx stuff...any damn calculation works in less than 8 seconds.:satisfie:

Some thing like (2456*4567 - 2134*3214)/2134*3214 will taken 10 seconds maximum...
it works coz I had that time 1.5 years ago..and I aint kidding..


Lets take one more.
Example 3: 532/745?
Tough???

This's how it can be approached:
# Nearest station.........750.................so add 5..............about 1% or less..add 1% damnit
# Numerator now is 537.............(added 1%)
# Fraction is 537/750 add 1/3 each...........it is 71 something.

Remember here don't even attempt to do...537/3. Because denominator is a 1000 and not a 100. So one digit is redundant. So all I do is........53/3 approx..18...plus..53 = 71%..(will do if answer are spaced...)

answers not spaced? Then 537 +537/3 = 537+179 = 716 which makes it 71.6 (calculator is 71.5)

Dont worry if the last few statements were difficult to digest. Try solving a few questions and you'll get the crux of it.

Remember in CAT we don't find answers... we choose them!
Happy Computing