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⁞ Chain Rule

Aptitude ➤ Chain Rule ➤ 1
Question 1
Q1.  If 20 pens cost Rs. 100, What do 45 pen cost ?
 

Answer :  Rs. 225


Let the required cost be Rs. x. Then ,

More Pens, More Cost (Direct Proportion)

∴ 20 : 45 :: 100 : x
⇒ 20 × x = 45 × 100
⇒ x = (45 × 100)/20 = Rs. 225


⚔ DISCUSS
Question 2
Q2.  If 6 men can do a piece of work in 30 hours, in how many hours will 15 men do it?
 

Answer :  12 hours


Let the required number of hours be x. Then ,

More men, less hours (Indirect Proportion)

∴ 15 : 6 :: 30 : x
⇒ 15 × x = 6 × 30
⇒ x = (6 × 30)/15 = 12 hours.


⚔ DISCUSS
Question 3
Q3.  If 20 men can build a wall 56 metres long in 6 days, what lenght of a similar wall can be built by 35 men in 3 days ?
 

Answer :  49 m


Let the required lenght be x metres. Then ,

More men, more lenght built(Direct Proportion)
Less Days, less lenght built (Direct Proportion)



∴ 20 × 6 × x = 35 × 3 × 56
⇒ x = (35 × 3 × 56)/120 = 49

Hence, the required lenght is 49 m.


⚔ DISCUSS
Question 4
Q4.  10 men working 6 hours a day can complete a work in 18 days. How many hours a day must 15 men work to complete the same work in 12 days ?
 

Answer :  6


Let the required number of hours per day be x hours. Then ,

More men, less hours per day (Indirect Proportion)
Less Days, more hours per day (Indirect Proportion)



∴ 15 × 12 × x = 10 × 18 × 6
⇒ x = (10 × 18 × 6)/(15 × 12) = 6

Hence, the required number of hours is 6 hours.


⚔ DISCUSS
Question 5
Q5.  If 7 spiders make 7 webs in 7 days, then 1 spider will make 1 web in how many days ?
 

Answer :  1


Let the required number of days be x . Then ,

Less spiders, More days(Indirect Proportion)
Less Webs, Less days (Direct Proportion)



∴ 1 × 7 × x = 7 × 1 × 7
⇒ x = (7 × 1 × 7)/7 = 7

Hence, the required number of days is 6 days.


⚔ DISCUSS
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