Successive Change or AB Method
Q1. |
A dealer sells his goods to a retailer at a profit of 5% and the retailer sells it to a customer at a profit of 10%. By how much percentage is the customer’s price more than the dealer’s price? |
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A. 16% |
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B. 20% |
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C. 15.5% |
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D. 16.5% |
Correct Option is C
Explanation:
Apply AB Method.
5 + 10 + 5*10/100 = 15.5
The customer’s price is 15.5% more than the dealer’s price.
Q2. |
A certain sum is invested at 10% p.a. for 2 years at compound interest. What will be the net percentage return on the sum invested? |
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A. 21% |
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B. 20.5% |
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C. 22% |
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D. 20% |
Correct Option is A
Explanation:
Compound interest is calculated on the amount.
Hence its is a case of successive change and we can apply AB Method.
10 + 10 + 10*10/100 = 21
21% return on investment
Q3. |
Two successive discounts of 20 % and 25 % are equivalent to a single discount of what %? |
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A. 45% |
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B. 50% |
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C. 40% |
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D. 55% |
Correct Option is C
Explanation:
Apply AB Method.
- 20 - 25 + 20*25/100 = -40
-40 indicates 40% discount
Q4. |
The value of an article is decreased by 10% and again decreased by 10%. What is the net effect on its price? |
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A. 19% increase |
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B. 29% decrease |
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C. 20% decrease |
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D. 19% decrease |
Correct Option is D
Explanation:
Apply AB Method.
- 10 - 10 + 10*10/100 = -19
-19 indicates 19% decrease in the net price
Q5. |
The price of petrol is increased by 30% and then decreased by 20%. What is the net effect on its price? |
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A. 4% decrease |
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B. 4% increase |
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C. 2% increase |
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D. 6% increase |
Correct Option is B
Explanation:
Apply AB Method.
30 - 20 - 30*20/100 = 4
4% increase
Q6. |
The price of an article is increased by 20% and later it is decreased by 20%. Find the overall percentage change in the price? |
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A. 4% increase |
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B. No change |
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C. 2% decrease |
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D. 4% decrease |
Correct Option is D
Explanation:
Apply AB Method.
10 - 20 - 20*20/100 = - 4
- 4 indicates 4% decrease in the price
Q7. |
The salary of a worker first increase by 10% and later decrease by 10%. What is the net effect on his salary? |
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A. No change |
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B. 1% increase |
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C. 1% decrease |
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D. 0.1% decrease |
Correct Option is C
Explanation:
Apply AB Method.
10 - 10 - 10*10/100 = - 1
1% decrease
Q8. |
The price of onion increases by 200% and therefore a family decreases its consumption by 50%. By how much percentage will the expenditure on onion change? |
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A. 50% increase |
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B. 100% increase |
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C. 50% decrease |
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D. 140% increase |
Correct Option is A
Explanation:
Apply AB Method.
200 - 50 - 200*50/100 = 50%
50% increase
Q9. |
The price of cooking oil increases by 60% and therefore a family decreases its consumption by 20%. By how much percentage will the expenditure on cooking oil change? |
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A. 38% increase |
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B. 28% decrease |
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C. 18% increase |
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D. 28% increase |
Correct Option is D
Explanation:
Apply AB Method.
60 - 20 - 60*20/100 = 28%
28% increase
Q10. |
The radius of a circle increases by 20%. By how much percentage will its area increase? |
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A. 42% |
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B. 44.4% |
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C. 44% |
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D. 44.2% |
Correct Option is C
Explanation:
Apply AB Method.
20 + 20 + 20*20/100 = 44%
Q11. |
The side of a square increases by 10%. By how much percentage will its area increase? |
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A. 20% |
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B. 19% |
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C. 22.1% |
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D. 21% |
Correct Option is D
Explanation:
Apply AB Method.
10 + 10 + 10*10/100 = 21%
Q12. |
The length of a rectangle increases by 20% and its breadth increases by 10%. By how much percentage will the area increase? |
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A. 30% |
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B. 32% |
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C. 33% |
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D. 31% |
Correct Option is B
Explanation:
Apply AB Method.
20 + 10 + 20*10/100 = 32%
Q1. |
Three successive discounts of 10%, 20% and 30% are equivalent to a single discount of ? (a) 25% (b) 28% (c) 23% (d) 26% |
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A. 46.9 % |
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B. 48.6% |
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C. 50.4% |
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D. 49.6 % |
Correct Option is D
Explanation:
For three successive discounts, we need to apply the AB method twice.
- 10- 20 + 10*20/100 = -
28
- 28 - 30+ 28*30/100 = - 49.6
- 49.6 indicates 49.6 % discount
Q2. |
The length, breadth, and height of a cuboid increase by 20%, 10%, and 10% respectively. By how much% will the volume increase? |
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A. 42% |
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B. 45.2% |
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C. 42.5% |
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D. 60% |
Correct Option is B
Explanation:
Volume = l × b × h
There are 3 dimension, we need to apply AB method twice
20 + 10 + 20*10/100 = 32
32 + 10 + 32*10/100 = 45.2%
Hence the volume will increase by 45.2%
Q3. |
The price of petrol increases by 25%, a man reduces consumption by such a percent so that his expenditure can only go up by 15%. By what % does he decrease his consumption? |
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A. 10% |
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B. 8% |
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C. 6.25% |
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D. 5% |
Correct Option is B
Explanation:
Apply AB Method.
In this question decrease percentage consumption is asked. Let’s take it ‘x’
25 – x – 25*x / 100 = 15
– 5x/4 = – 10
X = 40/5
x = 8 %
Note: To solve these kinds of questions where either A or B (of AB method) is asked, you can use the hit and trial (Options elimination process) method to get the answer.
Ex. If we apply the first option i.e. 10%,
25 - 10 - 25*10/100 = 12.5% (net result must be 15. hence eliminated)
If we apply the second option i.e. 8%,
25 - 8 - 25*8/100 = 15% (net result must be 15. hence is the answer)
Q4. |
The price of petrol increases by 30%, a man reduces consumption by such a percent so that his expenditure can only go up by 10%. By what % does he decrease his consumption? |
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A. 20% |
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B. 17% |
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C. 43% |
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D. 15.38% |
Correct Option is D
Explanation:
Apply AB Method.
In this question decrease, the percentage of consumption is asked. Let’s take it ‘x’
30 – x – 30*x / 100 = 10
– 13x/10 = – 20
X = 200/13
x = 15.38 %
Note: To solve these kinds of questions where either A or B (of AB method) is asked, you can use the hit and trial (Options elimination process) method to get the answer.
Ex. If we apply the first option i.e. 20%,
30 - 20 - 30*20/100 = 4% (net result must be 10. hence eliminated)
Similarly, other options can be applied.
Q5. |
A shopkeeper marks his goods 50% above his cost price and allows a discount of 20%. What percentage profit does he make? |
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A. 30% |
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B. 20% |
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C. 25% |
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D. 15% |
Correct Option is B
Explanation:
It is a case of successive change.
Apply AB Method.
50 - 20 - 50*20/100 = 20
The shopkeeper makes a profit of 20%