Inplant Training for Electronics and Communication Engineering Students in Annanagar chennai - By 10 Times Microsoft Awarded MVP

Percentage

Important Formulae

1. Concept of Percentage:

By a certain percent, we mean that many hundredths.
Thus, x percent means x hundredths, written as x%
To express x% as a fraction: We have, x% = x/100
Thus, 20% =20/100 = 1/5.
To express a/b as a percent: We have a/b=(a/b)*100%

2. Percentage Increase/Decrease::

If the price of a commodity increases by R%, then the reduction in consumption so as not to increase the expenditure is:

[(R/(100+R))*100]%

If the price of a commodity decreases by R%, then the increase in consumption so as not to decrease the expenditure is:

[(R/(100-R))*100]%

3. Results on Population:

Let the population of a town be P now and suppose it increases at the rate of R% per annum, then:

1. Population after n years = P[1+(R/100)]^n
2. Population n years ago =P/[1+(R/100)]^n

4. Results on Depreciation:

Let the present value of a machine be P. Suppose it depreciates at the rate of R% per annum. Then:

1. Value of the machine after n years = P[1-(R/100)]^n
2. Value of the machine n years ago = P/[1-(R/100)]^n
3. If A is R% more than B, then B is less than A by {[R/(100+R)]*100}%
4. If A is R% less than B, then B is more than A by {[R/(100-R)]*100}%

General Tips

When any value increases by
10%, it becomes 1.1 times of itself. (since 100+10 = 110% = 1.1)
20%, it becomes 1.2 times of itself.
36%, it becomes 1.36 times of itself.
4%, it becomes 1.04 times of itself.
Thus we can see the effects on the values due to various percentage increases.
When any value decreases by
10%, it becomes 0.9 times of itself. (Since 100-10 = 90% = 0.9)
20%, it becomes 0.8 times of itself
36%, it becomes 0.64 times of itself
4%, it becomes 0.96 times of itself.
Thus we can see the effects on a value due to various percentage decreases.
NOTE:
1. When a value is multiplied by a decimal more than 1 it will be increased and when multiplied by less than 1 it will be decreased.
2. The percentage increase or decrease depends on the decimal multiplied.
Eg: 0.7 => 30% decrease, 0.67 => 33% decrease, 0. 956 => 4.4% decrease and so on.