Question

In what proportion water must be added to
milk to gain -25% by selling it at the cost
price ?​

Answer 1

Answer:

Let’s assume the C.P. of 1 litre of milk be Re. 1

So, S.P. of 1-litre mixture = Re. 1 [since C.P. of 1 – litre water is zero]

Gain% = 25%

∴ C.P. of 1-litre mixture,

= [100/(100*G%)*S.P.]

= [100/(100*25%)*S.P.]

= [100/125] * 1

= Re. 4/5

Therefore, by using mixture and alligation, we get

C.P. of 1-litre water                        C.P. of 1-litre milk

                       0                                1

                            \                         /

                               \                   /

                                 \              /

                        C.P. of 1-litre mixture

                                     4/5

                                      / \

                                   /       \

                                /             \

                               1/5           4/5

Thus,  

The ratio of water & milk = 1/5 : 4/5 = 1 : 4.

Answer 2

Answer:

1 : 4  is the ratio in which water must be added to

milk

Step-by-step explanation:

Let say cost Price of Milk  = Rs C per litre

Let say W liter water is added per Litre

Then Total Milk  = 1 + W

Selling Price = C(1 + W)

Cost Price = C

Profit = C(1 + W) - C  = CW

Profit % = (CW/C) * 100  = 100W

100W = 25

=> W = 1/4

1/4 Water is added in 1 litre Milk

=> 1 litre Water is added in 4 litre milk

1 : 4  is the ratio in which water must be added to

milk