Question

Due to 25% rise in the price of milk, the milkman is able to
purchase 20 liters less of milk for Rs. 4000. Find the original
price of milk.​

Answer 1

Answer:

40 Rs.

Step-by-step explanation:

Let Original Price = P

Original Quantity = Q

P X Q = 4000 ….( I )

New price = (5/4)P

New quantity = (Q-20)

(5/4)P X (Q-20) = 4000 …. ( II )

(5/4) * 4000 / Q *(Q-20 ) = 4000

5 * (Q - 20) = 4Q

5Q - 100 = 4Q

Q = 100

Put the value of Q in equation (I) , we get

P = 4000/100

P = 40 Rs.

Answer 2

Let the initial price be X and consumption of milk be Y

At first, X × Y = 400    - (1)

price is raised by 25%,

X+ 25% of X

• For Rs.4000 the milkman is able to purchase 20l less cause of the price hike.
• So modify the equation from (1) as per the milk rise and 20l less consumption.

(X+ 25% of X) × (Y-20) = 4000

(X+0.25 OF X) × (Y-20) = 4000     -(2)

Now divide (2)/ (1), we get

$\frac{(1.25 X) \times(Y-20)}{X\times Y} = \frac{4000}{4000}$

we know that 1.25= 5/4

5Y-100=4Y

Y=100

put value of Y in equation 1

X×100 = 4000

X = 40

Hence  Rs.40 per liter is the original price of the milk.