Q18 of 83 Page 90

If the price of petrol is increased by Rs. 5 per litre. One gets 2 litres less petrol spending Rs. 1320. What is the increased price of the petrol?

Let original price of 1 ltr. Petrol bex.


If price increased by Rs.5 per ltr.


⇒ New price = x + 5 per ltr.


Given, one gets 2 ltr. Petrol for Rs.1320.



⇒ 1320(x + 5) – 1320x = 2x(x + 5)


⇒ 1320x + 6600x – 1320x – 2 x2 + 10x = 0


⇒ 2x2 + 10x – 6600 = 0


Dividing the equation by 2, we get –


⇒x2 + 5x – 3300 = 0


⇒x2 + (60 – 55)x – 3300 = 0


⇒x2 + 60x – 55x – 3300 = 0


⇒ x(x + 60) – 55(x + 60) = 0


⇒ x = – 60 or x = 55


But price cannot be negative.


⇒ x = Rs.55/ltr.


And increased price = 60/ltr.


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