Please help!

A service station has 2 kinds of oil, one selling for $1.27/litre and the other for $1.18/litre. How many litres of each must be used to make 90 litres of a mixture that can be sold for $1.24/litre?

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- Jul 20th 2007, 11:01 PM #1

- Jul 20th 2007, 11:08 PM #2

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- Jul 20th 2007, 11:13 PM #3
Hello,

let x be the amount of oil which is sold for $1.27

then (90-x) is the amount of oil which is sold for $1.18.

Now you can set up the equation:

$\displaystyle x \cdot 1.27 - (90-x) \cdot 1.18 = 90 \cdot 1.24$ . Expand the bracket and collect like terms :

$\displaystyle x \cdot 1.27 - x \cdot 1.18 = 90 \cdot 1.24 - 90 \cdot 1.18$

$\displaystyle x \cdot 0.09 = 5.4$ . Divide both sides of the equation by 0.09 and you'll get:

$\displaystyle x = 60$

That means: Take 60 ltrs of the $1.27-oil and 30 ltrs of the $1.18-oil to get the mixture which you can sell for $1.24