Large, medium and small ships are used to bring water. 4 large ships carry as much water as 7 small ships. 3 medium ships carry the same amount of water as 2 large ships and 1 small ship. 15 large, 7 medium and 14 small ships, each made 36 journeys and brought a certain quantity of water.In how many journeys would 12 large, 14 medium and 21 small ships bring the same quantity?

Let $$L$$ = Large ships, $$M$$ = Medium ships and $$S$$ = Small ships

According to ques, => $$4L=7S$$

=> $$\frac{L}{S}=\frac{7}{4}$$

=> $$L=7x$$ and $$S=4x$$

Also, $$3M=2L+S$$

=> $$M=\frac{2\times7x+4x}{3}=6x$$

Thus, ratio of large : medium : small = 7:6:4

$$\therefore$$ Number of journeys required = $$\frac{(15\times7)+(7\times6)+(14\times4)}{(12\times7)+(14\times6)+(21\times4)}\times36$$

= $$\frac{7308}{252}=29$$

=> Ans - (C)