Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms of oil are added to the 8 kilograms mixture A, how many kilograms of mixture A must be added to make a 70% material B in the new mixture?  Choose the correct choice:  A) 6  B) 7  C) 8  D) 9  E) 10
Old mix has 20% oil. You add 2 kgs of 100% oil. You get new mix with 30% oil (70% material B).   w1/w2 = (100 - 30)/(30 - 20) = 70/10= 
<gadget id="calculator">70/10</gadget>
<output>7</output>
7/1   For every 7 parts of mix A, you have added 1 part of oil. Since you have added 2 kgs oil, mix A must be 7*2= 
<gadget id="calculator">7*2</gadget>
<output>14</output>
14 kgs.   You already had 8 kgs of mix A, so extra mix A added must be 14 - 8= 
<gadget id="calculator">14 - 8</gadget>
<output>6</output>
6 kgs.   6nswer (6)
<result>A</result>
Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms of oil are added to the 8 kilograms mixture A, how many kilograms of mixture A must be added to make a 70% material B in the new mixture?