Chain Rule Problems and Solutions

• 8. 4 mat-weavers can weave 4 mats in 4 days. At the same rate, how many mats would be woven by 8 mat weavers in 8 days ?

  1. 12
  2. 14
  3. 16
  4. 18

  Answer :

  Option C

  Explanation:

  Please always remember, that what exactly we need to calculate before applying chain formula. As in this question we need to find how many mats, RIGHT !
  So we will compare everything with "number of mats"
  As,
  
  More men, More number of mats (Direct Proportion)
  More days, More number of mats (Direct Proportion)
  
  So, it can be solved as,
  
  \begin{aligned}
  \begin{bmatrix}Weavers & 4 & 8 \\Days & 4 & 8 \end{bmatrix} :: 4 : x \\
  
  => x*4*4 = 8*8*4 \\
  => x = 16
  \end{aligned}

• 9. If the cost of x metres of wire is d rupees, then what is the cost of y metres of wire at the same rate ?

  1. xd
  2. yd
  3. yd/x
  4. x/yd

  Answer :

  Option C

• 10. If the price of 23 toys is 276, then what will the price of 12 toys ?

  1. 144
  2. 148
  3. 156
  4. 186

  Answer :

  Option A

  Explanation:

  Less toys, Less Price (Direct Proportion)
  So, let the price be Rs. x
  then,
  \begin{aligned}
  23:12 :: 276:x
  => x = \frac{276*12}{23} \\
  => x = 144
  \end{aligned}
  
  So price of 12 toys will be Rs. 144

• 11. 36 men can complete a piece of work in 18 days. In how many days will 27 men complete the same work ?

  1. 24 days
  2. 28 days
  3. 34 days
  4. 35 days

  Answer :

  Option A

  Explanation:

  Less Men, means more Days {Indirect Proportion}
  
  Let the number of days be x
  then,
  
  27 : 36 :: 18 : x
  [Please pay attention, we have written 27 : 36 rather than 36 : 27, in indirect proportion, if you get it then chain rule is clear to you :)]
  
  \begin{aligned}
  x = \frac{36*18}{27} \\
  x = 24
  \end{aligned}
  So 24 days will be required to get work done by 27 men.