Question

one dozen of bananas were available in a particular price. At present only 10 bananas are available in that price. Increase in price is?

Answer 1

If the cost of bananas is increased by 10 Rs per dozen, one can get 3 dozen less for 600 Rs. What is the original cost of the bananas?
Let x be the original cost of a dozen bananas. For Rs.600 let us one gets y dozens.

xy = 600 … (1)

(x+10)(y-3) = 600 … (2)

From (1) y = 600/x. Putting that value in (2), we get,

(x+10)(600/x-3) = 600 or

(x+10)(600–3x)/x = 600 or

(10+x)(600 -3x) = 600x or

6000 + 570x - 3x^2 = 600x or

6000 - 30x - 3x^2 = 0 or

2000 - 10x - x^2 = 0

x^2 + 10x - 2000 = 0

(x+50)(x-40) = 0

So x = -50 or 40. Since cost of bananas cannot a negative figure, x = 40.

So at Rs.40 per dozen one can buy 15 dozens for Rs.600. If the cost goes up by Rs.10, the person can get 600/(40+10) = 600/50 = 12 dozens which is 3 dozens short of the previous purchasing power!

So the original cost of bananas is Rs.40 per dozen.

Answer 2

Let the cost of dozen of banana be X.
Then,
12banana cost =Rs.X
1 banana cost=Rs.X/12
•°•10 banana cost =Rs.X×10/12
Increase in price =5X/6