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Chain Rules - Online Quiz

Following quiz provides Multiple Choice Questions (MCQs) related to Chain Rules. You will have to read all the given answers and click over the correct answer. If you are not sure about the answer then you can check the answer using Show Answer button. You can use Next Quiz button to check new set of questions in the quiz.

Q 1 - If 21 cows eat as much as 15 buffaloes, how many cows will eat as much as 35 buffaloes?

Answer : A

Explanation

15 buffaloes = 21 cows ⇒ 1 buffalo = 21/15 cows = 7/5 cows
⇒35 buffaloes = (35 * 7/5 ) cows = 49 cows.

Q 2 - A tree 6m tall casts a 4m long shadow. At the same times, a flagpole casts a 50 m long shadow. How long is the flagpole?

Answer : B

Explanation

Let the length of the flagpole be x metres.
Longer is the shadow, longer is the object (Direct)
4: 50 :: 6:x ⇒ 4x = (50 * 6 ) ⇒ x= (50*6 )/4 =75m.
Length of flagpole = 75m.

Q 3 - If 12 men or 18 women can do a piece of work in 14 days , how long will 8 men and 16 women take to finish the work?

Answer : A

Explanation

12 men = 18  women ⇒ 1 man = 18/12 women
⇒ 8 men = (18/12 * 8) women = 12 women
⇒ (8 men + 16 women ) = 28 women
Let the required number of days be x.
More women, less days         (Indirect)
28: 18:: 14 : x ⇒ 28x = (18*14 ) ⇒ x= (18 *14) / 28 = 9days

Q 4 - 8 men and 12 children can do a piece of work in 9 days . A child takes double the time to do a work than the men. In how many days 12 men can complete the work?

Answer : A

Explanation

2 children = 1 men ⇒ (8 men + 12 children ) = 14 men.
Let the required number of days be x. 
Less men , more day       (Indirect )
12 : 14:: 9 : x ⇒ 12x = ( 14 * 90 ⇒ ( 14* 9 ) /12 = 21 /2 = 21/2 days.

Q 5 - If a job takes 12 workers 4 hours to complete, how long should it take 15 workers to complete the job?

Answer : C

Explanation

Let the required number of  hours b x.
More working , less  hours             (Indirect)
15 : 12 :: 4 : x = > 15 x = ( 12 * 4 ) ⇒ x= (12 * 4 ) /15 = 16 / 5 hrs = 3hrs 12 min.

Q 6 - A contractor undertakes to build a wall in 50 days. He employs 50 people for the same . However, after 25 days , he finds that only 40 % of the work is complete , How many more men need to be employed to complete the work in time?

Answer : B

Explanation

Work done = 40/100 = 2/5 , Remaining work = ( 1 - 2/5 ) = 3/5.
2/5 work is done in 25 days by 50 people.
3/5 work will be done in 25 days by (50 * 5/ 2 * 3/5) people = 75 people.
Required number of people = ( 75 ? 50 )  = 25.

Q 7 - 400 persons working 9 hours per day complete 1/4 th of the work in 10 days . The number of additional persons , working 8 hours per day required to complete the remaining work in 20 days , is:

Answer : D

Explanation

Let the number of additional men be x .
Less hrs per days, more men       ( Indirect)
More days , less men              ( Indirect)
More work, more men         ( Direct)
Her/ days   8:9
Days    20 : 10
:: 400 : ( 400 + x ) 
Work 1/4 : 3/4
∴ 8 * 20 * 1/4 * ( 400 + x ) = 9 * 10 * 3/4 * 400
⇒ ( 400 + x ) = 9 * 10 * 3 * 400/ 8 * 20  = 675.
Number of  additional men = 675.

Q 8 - If 42 persons consume 144kg of rice in 15 days , then in how many days will 30 persons consume 48kg of rice?

Answer : D

Explanation

Let the required  number of  days be x.
More persons, more  days       (Direct)
Less rice, less days         (Indirect)
Persons     30 : 42  
:: 15 : x
Quantity     144 :  48 
∴ ( 30 * 144 * x ) = ( 42 * 48 *15 ) ⇒ x = 42 * 48 * 15/ 30 * 144 = 7 days

Q 9 - 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 . 8 men and 6 boys can do 3 times the amount of this work in

Answer : A

Explanation

Let 1 men 1 days work be 1/x and 1 boy 1 day work be 1/y
Then 2/x + 7/y = 1/14 ⇒ 2u + 7v = 1/14 -(i) When u= 1/x, v=1/y.
3/x +8/y =1/11 ⇒ 3u + 8v = 1/11?.(ii)
Multiplying (i) by (ii) by 2 and subtracting , we get:
5v = ( 3/14 ? 2/11) = 5/ 154 ⇒ v = 1/154
Putting v = 1/154 in (i) we get : 2u +7* 1/154 = 1/14
∴ 2u = (1/14- 1/22)= (11-7/54) = 4/154 = 2/77 ⇒ u=1/77.
(8 men +6 boys) 1 days work = (8/77 +6/154 ) = 22/154 = 1/7.
∴ 8men and 6 boys can do it in 7 days.
They will do thrice of this work in (3*7) days = 21days.

Q 10 - A contractor undertook to do a certain piece of work in 9 days. He employed certain number of labourers. But , 6 of them being absent from the very first day ,the rest could finish the work in 15 days. The number of men originally employed were?

Answer : B

Explanation

let there be x men at the beginning.
Less men , more days     (indirect)
15:9 :: x : (x-6)⇒ 15 (x-6) = 9x ⇒ 6x = 90 ⇒x=15 men.

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