Chain Rule problems
- 1. If the price of 23 toys is 276, then what will the price of 12 toys ?
Options- A. 144
- B. 148
- C. 156
- D. 186 Discuss
Correct Answer: 144
Explanation:
Less toys, Less Price (Direct Proportion)
So, let the price be Rs. x
then,
23:12::276:x => x=(276*12)/23
=> x=144
So price of 12 toys will be Rs. 144
- 2. If 20 men can build a wall 56 meters long in 6 days , what length of a similar wall can be built by 35 men in 3 days?
Options- A. 46
- B. 47
- C. 48
- D. 49 Discuss
Correct Answer: 49
Explanation:
Let the required length be x meters
More men, More length built (Direct proportion)
Less days, Less length built (Direct Proportion)
=> (20 x 6 x X)=(35 x 3 x 56)
=> x = 49
Hence, the required length is 49 m.
- 3. A certain number of men can finish a piece of work in 100 days. If there were 10 men less, it would take 10 days more for the work to be finished. How many men were there originally?
Options- A. 75
- B. 82
- C. 100
- D. 110 Discuss
Correct Answer: 110
Explanation:
Originally let there be x men.
Less men, More days (Indirect Proportion)
Therefore, (x-10) : x :: 100 :110
=> (x - 10) * 110 = x * 100 => x= 110
- 4. If 36 men can do a piece of work in 25 hours, in how mwny hours will15 men do it?
Options- A. 40
- B. 50
- C. 60
- D. 70 Discuss
Correct Answer: 60
Explanation:
Let the required no of hours be x. Then
Less men , More hours (Indirct Proportion)
Therefore, 15:36 ::25:x
=> (15 x X)=(36 x 25) => x = 60
Hence, 15 men can do it in 60 hours.
- 5. 2 men and 7 boys can do a piece of work in 14 days; 3 men and 8 boys can do the same in 11 days. Then, 8 men and 6 boys can do three times the amount of this work in
Options- A. 18 days
- B. 21 days
- C. 24 days
- D. 30 days Discuss
Correct Answer: 21 days
Explanation:
(2 x 14) men +(7 x 14) boys = (3 x 11) men + (8 x 11) boys
=>5 men= 10 boys => 1man= 2 boys
Therefore, (2 men+ 7 boys) = (2 x 2 +7) boys = 11 boys
( 8 men + 6 boys) = (8 x 2 +6) boys = 22 boys.
Let the required number of days be x.
More boys , Less days (Indirect proportion)
More work , More days (Direct proportion)
Therefore, (22 * 1 * x) = (11 * 3 * 14)
=> x = 21
Hence, the required number of days = 21
- 6. If 7 spiders make 7 webs in 7 days, then 1 spider will make 1 web in how many days?
Options- A. 1
- B. 3
- C. 7
- D. 14 Discuss
Correct Answer: 7
Explanation:
Let the required number days be x.
Less spiders, More days (Indirect Proportion)
Less webs, Less days (Direct Proportion)
=> 1 * 7 * x = 7 * 1 * 7
=> x= 7
- 7. A contractor undertakes to do a piece of work in 40 days. He engages 100 men at the begining and 100 more after 35 days and completes the work in stipulated time. If he had not engaged the additional men, how many days behind schedule would it be finished?
Options- A. 3
- B. 5
- C. 6
- D. 9 Discuss
Correct Answer: 5
Explanation:
[(100 x 35) + (200 x 5)]men can finish the work in 1 day
Therefore, 4500 men can finish the work in 1 day. 100 men can finish it in 4500/100= 45 days.
This is 5 days behind Schedule
- 8. 39 persons can repair a road in 12 days, working 5 hours a day. In how many days will 30 persons, working 6 hours a day, complete the work?
Options- A. 10
- B. 13
- C. 14
- D. 15 Discuss
Correct Answer: 13
Explanation:
Let the required number of days be x.
Less persons, More days (Indirect Proportion)
More working hours per day, Less days (Indirect Proportion)
=> 30 * 6 * x = 39 * 5 * 12
=> x= 13
- 9. 3 pumps working 8 hours a day, can empty a tank in 2 days. How many hours a day must 4 pumps work to empty the tank in 1 day?
Options- A. 9
- B. 10
- C. 11
- D. 12 Discuss
Correct Answer: 12
Explanation:
Let the required no of working hours per day be x.
More pumps , Less working hours per day (Indirect Proportion)
Less days, More working hours per day (Indirect Proportion)
=> (4 * 1 * x) = (3 * 2 * 8)
=> x=12
- 10. If 18 bindres bind 900 books in 10 days , How many binders will be required to bind 660 books in 12 days?
Options- A. 22
- B. 14
- C. 13
- D. 11 Discuss
Correct Answer: 11
Explanation:
Let the required no of binders be X.
Less books , Less binders (Direct Proportion)
More days, Less binders (Indirect proportion)
Therefore, (900 * 12 * x) = (660 * 10 * 18)
=> x = 11
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