Question

rohit bought 20 oranges and 30 bananas for RS280 . if the cost of each orange got doubled , then he would have bought 30 oranges and 40 bananas for RS 540.find the cost of each orange.(in RS)

Answer 1

Let cost of each orange = Rs. x
     cost of each banana = Rs. y
Cost of 20 oranges and 30 bananas = 20x+30y
So 20x+30y = 280
⇒ 2x + 3y = 28

if cost of each orange is doubles, cost of each orange = 2x
cost of 30 oranges and 40 bananas = 30(2x) + 40y  = 60x+40y
thus 60x+40y = 540
⇒6x + 4y = 54

Solving the two equations we get, x = 5 and y = 6.
 So cost of each orange = Rs. 5.

Answer 2

Let the cost of each orange be Rs x
Cost of each banana = Rs y

Cost of 20 oranges and 30 bananas = 280
⇒20x+30y = 280
Dividing both sides by 10
⇒ 2x + 3y = 28 ........(1)

Cost of each orange is doubled.
Now, cost of orange = Rs 2x
Cost of 30 oranges and 40 bananas is Rs 540
60x + 40y = 540
Dividing both sides by 20
3x + 2y = 27 .......(2)

Multiply eq (1) by 2 and eq(2) by 3

4x + 6y = 56
9x + 6y = 81         (Subtract)
-----------------         
 -5x = - 25

x = 5

Cost of each organge = Rs 5