SOLUTION: the cost of petrol rises by 2 naira per litre. last week a motorist bought 25 litres at the old prices. this week she bought 20 litres at new price. altogether, the petrol cost 364

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: the cost of petrol rises by 2 naira per litre. last week a motorist bought 25 litres at the old prices. this week she bought 20 litres at new price. altogether, the petrol cost 364      Log On


   

Question 1033437: the cost of petrol rises by 2 naira per litre. last week a motorist bought 25 litres at the old prices. this week she bought 20 litres at new price. altogether, the petrol cost 3640 naira. what was the old price for 1 litre
Answer by Theo(13342) About Me  (Show Source):
You can put this solution on YOUR website!
let x = the old price.
then x + 2 = the new price.

25 * x + 20 * (x+2) = 3640

simplify to get 25 * x + 20 * x + 40 = 3640

combine like terms to get 45 * x + 40 = 3640

subtract 40 from both sides of the equation to get 45 * x = 3600

divide both sides of the equation by 45 to get x = 80.

the old price per liter is 80.
the new price per liter is 82.

25 * 80 + 20 * 82 = 3640.

old price per liter is 80 naira.