Question 1163594
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<pre>

Let x be the first amount of oil, poured out (in kilograms).


Then the rest was 3x kilograms.


Second pour out was  {{{(2/5)*3x}}} = {{{(6/5)x}}} kilograms.


We are given that the difference was 0.25 kilograms :


    {{{(6/5)x}}} - x = 0.25.


From this point, there is one step to get the answer


    {{{(1/5)x}}} = 0.25

    x = 5*0.25 = 1.25 kilograms.


<U>ANSWER</U>.  1,25 kg was poured out the first time.
</pre>

Solved.


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The major lesson to learn from my solution is how I choose my major unknown.


I choose it in this way  to avoid working with the forest of fractions.