Question 1055367
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Fifteen litres of fuel containing  3.2% oil is available for a certain two-cycle engine. 
This fuel is to be used for another engine requiring a  5.5% oil mixture. How many litres of oil must be added?
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<pre>
The basic equation is 

{{{(15*0.032 + v)/(15 + v)}}} = 0.055.   (1)

To solve it, multiply both sides by (15 + v). You will get

15*0.032 + v = 0.055*(15+v),

0.48 + v = 0.825 + 0.055v,

v - 0.055v = 0.825-0.48,

0.945v = 0.345  --->  v = {{{0.345/0.945}}} = 0.365.

<U>Answer</U>.  0.365 liters of oil must be added.
</pre>

Be aware: Writing by josgarithmetic on this problem is absolutely wrong starting from his first equation.