In this post I describe some of the tricks of percentage calculation .
by a certain percent , we means that many hundredths thus , x percent means x hundredths written as x%
Fraction value of percentage :
1/2 = 50 % 1/3 = 33.33% 1/4 = 25% 1/5 = 20 %
1/6 =16.67% 1/7 = 14.28% 1/8 =12.5% 1/9 = 11.11
Note :these fraction value helps to minimize the calculation
Formula:
- if the price of a commodity increases by R% , then the reduction in consumption so as not to increase the expenditure is 100*R/(100+R)%.
- if the price of a commodity decreases by R% , then the increases n consumption so as not to decreases the expenditure is 100*R/(100-R)%.
- value of machine after n years = p(1-R/100)power n .
- if A is R% more than B , then b is less than A by 100*R/(100+R)%.
- if A is R% less than B , then b is more than A by 100*R/(100-R)%.
Example:
1. if 1/5 of a number is 25 less then 1/4 of a same number . what will be 3/2 of number .
ans.
as you know 1/5 = 20% and 1/4 = 25%
so difference b/w these two is 5% which is equal to 25
then 5% *20 ---- 25*20 100% ----500
and 100% percent is the real value
you can now calculate 3/2 so ans is 750
2. if the numerator of fraction is increase by 20% and denominator is decrease by 80% then fraction becomes 18/15. what is the actual fraction .
ans . 120% N/20% D = 18/15
then N/D = (18/15 )*20/120
N/D = 1/5 answer
3 . if A's salary 20% less then B's salary then B's salary is how much more then A.
ans . suppose B's salary is 100 then A's salary is 80
now you can calculate b's salary in respect to A
( 20/80)* 100 = 25% is answer
4. A
number is increased by 12% and again deceased by 18% then how much change in that value.
formula for this problem % change = (x)+(y)+x*y/100
Note take the value with symbol , if increase then take '"plus" if decease in value then take "minus". this formula is applicable for circle , square , triangle etc
12- 18 - 216/100 = -8.16 decrease is value by 8.16%
