SOLUTION: if the price of kerosene is increased by $6 per litre, find the new price per litre if two-thirds of the new price is equal to five-sevenths of the old price
Question 1191411: if the price of kerosene is increased by $6 per litre, find the new price per litre if two-thirds of the new price is equal to five-sevenths of the old price Found 2 solutions by Theo, MathTherapy:Answer by Theo(13342) (Show Source): You can put this solution on YOUR website! x equals the new price.
y equals the old price.
x = y + 6
2/3 * x = 5/7 * y
multiply both sides of this equation by 3/2 to get:
x = 5/7 * 3/2 * y
simplify to get:
x = 15/14 * y
since x = y + 6, then you get:
y + 6 = 15/14 * y
subtract y from both sides of the equation to get:
6 = 15/14 * y - y
since 1 * y = 14 * y / 14, you get:
6 = 15/4 * y - 14/14 * y
simplify to get:
6 = 1/14 * y
solve for y to get:
y = 14 * 6 = 84
since x = y + 6, then you get:
x = 90
to confirm, you have:
x = y + 6 becomes 90 = 84 + 6 which is true.
2/3 * x = 5/7 * y becomes 2/3 * 90 = 5/7 * 84 which becomes 60 = 60 which is true.
this confirms the solution is correct.
the solution is that the new price is $90 per liter.
Let new price be N
Then old price = N - 6
Then we get:
7(2N) = 3(5N - 30) ----- Cross-multiplying
14N = 15N - 90
14N - 15N = - 90
- N = - 90
New price or
That's IT!!