a 6 litre sol is 20 % alcohol. how many litres of pure alcohol must be added to produce a sol that is 50 % alcohol?  Choose one.
A) a . 0.6 B) b . 1 C) c . 2.1 D) d . 3.6 E) e . 5.4
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 6</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">2 * (6/5)</gadget>
<output>12/5 = around 2.4</output>

<gadget id="calculator">6 - (12/5)</gadget>
<output>18/5 = around 3.6</output>

<result>D</result>
a 6 litre sol is 20 % alcohol. how many litres of pure alcohol must be added to produce a sol that is 50 % alcohol?
subtract(6, multiply(const_2, multiply(divide(20, const_100), 6)))
"20 % of 6 = 1.2 50 % of 6 = 3 shortage is 1.8 so we need to have 1.8 / 50 % to get 50 % alcohol content . = 3.6 d"