Short cut methods in quantitative aptitude
Todays all competitive exams are having the topics of quantitative aptitude and reasoning.If you know the solving method for particular problem in seconds,then you can said to be good in aptitude.In aptitude for every problem or question we have short cut methods.
Why and where to apply short cut methods
- in bank exams like IBPS
- Written test for MNC job
CAT,MAT,GRE,GATE ,railways exams,lic,all national level exams
formula or trick ?
we are not going to solve the problems in formula,hate formulas,try to solve in logical methods,which are not related to any formula.So we are giving you suggestion that,apply tricks,which improves your logical thinking and attitude
Where i have to learn these tricks to solve quantitative aptitude problems?
These methods/tricks will not available in any books or any other websites,no any website providing the short cut tricks to solve the problems in less time.In this site you can learn aptitude short cut methods
IBPS EXAM SPECIAL
Learn short cut methods in aptitude to get your dream job,so for every day,apply new methods to solve the problems by using our short cut methods.Start from here,the lessons for aptitude tricks from all topics.Today we are explaining you,short cut methods in percentage topic ,which related to aptitude.
LESSON 1 -SHORT CUT METHODS/TRICKS IN PERCENTAGES
Important Points to Note:
- 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.
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.
Eg: When the actual value is x, find the value when it is 30% decreased.
Soln: 30% decrease => 0.7 x.
Eg: A value after an increase of 20% became 600. What is the value?
Soln: 1.2x = 600 (since 20% increase)
ð x = 500.
Eg: If 600 is decrease by 20%, what is the new value?
Soln: new value = 0.8 X 600 = 480. (Since 20% decrease)
Thus depending on the decimal we can decide the % change and vice versa.
Eg: When a value is increased by 20%, by what percent should it be reduced to get the actual value?
Soln: (It is equivalent to 1.2 reduced to 1 and we can use % decrease formula)
% decrease = (1.2 – 1)/1.2 X 100 = 16.66%.
- When a value is subjected multiple changes, the overall effect of all the changes can be obtained by multiplying all the individual factors of the changes.
Eg: The population of a town increased by 10%, 20% and then decreased by 30%. The new population is what % of the original?
Soln: The overall effect = 1.1 X 1.2 X 0.7 (Since 10%, 20% increase and 30% decrease)
= 0.924 = 92.4%.
Eg: Two successive discounts of 10% and 20% are equal to a single discount of ___
Soln: Discount is same as decrease of price.
So, decrease = 0.9 X 0.8 = 0.72 => 28% decrease (Since only 72% is remaining).
- If 20% of 40% of a = 25% of a% of b, then what is b?
a. 8/5 b. 16/25 c. 8/25 d. None
2. By what % is 200 more than 50?
a. 100 b. 200 c. 300 d. None
3. A value changes from 30 to 80. What is the percentage change?
a. 125 b. 166.66 c. 156 d. None
4. The population of a city is increased by 30% and thus became 78000. What is the original population?
a. 76000 b. 64200 c. 60000 d. None
5. In a theatre, the number of seats is increased by 20% and the price per ticket is increased by 10% but the public response decreased by 30%. What is the net effect on the economy of the theatre?
a.10% rise b. 7% fall c. 7% rise d. None
6. A saves 20% of his income. His income is increased by 20% and so he increased his expenditure by 30%. What is the percentage change in his savings?
a. 20% fall b. 4% fall c. 20% rise d. 4% rise
7. The price of petrol is increased by 25%. By what percent the consumption be reduced to make the expenditure remain the same?
a. 25% b. 33.33% c. 20% d. None
8. The side of a square is increased by 20%. The percentage change in its area is ___
a. 20% b. 44% c. 36% d. None
9. If the length of a rectangle is increased by 33.33%, by what percentage should the breadth be reduced to make the area same?
a. 20% b. 33.33% c. 25% d. None
10. In an election between two candidates, A and B, A secured 56% of the votes and won by 48000 votes. Find the total number of votes polled if 20% of the votes were declared invalid.
a. 500000 b. 400000 c. 600000 d. None
clear explanation for above problems:
- 1/5 X 2/5 X a = ¼ X a X b => b = 8/25
- % difference = (200-50)/50 X 100 = 300 %
- % increase = (80-30)/30 X 100 = 166.66 %
- 1.3 x = 78000 => x = 60000.
- Net effect = 1.2 X 1.1 X 0.7
= 0.924 => 7.6% decrease.
- Let I be the income.
Expenditure = 0.8I Savings = 0.2I => 20%
New income = 1.2I (since 20% rise)
New expenditure = (0.8I) X 1.3 (Since 30% rise)
So, new savings = 1.2I – 1.04I = 0.16I => 16%
(So income decreased form 20% to 16%)
% decrease = (20-16)/20 X 100 = 20%.
- It is equivalent to 1.25 decreased to 1.
% decrease = (1.25-1)/1.25 X 100 = 20%
8. % change in area = 1.2 X 1.2 (since area = side X side)
= 1.44 => 44%.
- It is equivalent to 1.25 decreased to 1. So 20% decrease.
- Valid Votes:
A got 56% => B got 44%
Difference = 12% = 48000
So, 100% = 400000. These are valid votes.
But valid votes are only 80% of total votes.
So, 80% of total votes = 400000 => total votes = 500000
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