a bag of blue and green colored marbles has 50% green marbles, with a total of 40 marbles. how many green marbles need to be added to bring their percentage in the bag up to 80%? Choose the correct answer.
A) 60 B) 58 C) 42 D) 24 E) 80
A bag of 40 marbles which is 50% green marbles means we have 20 green marbles. To get a bag that is 80% green marbles, let's use this expression: (20 + x)/(40 + x) = 0.8 with x representing the amount of green marbles that must be added to get to 80%. The expression thus represents the new number of green marbles over the total new number of marbles and this fraction should equal 80%. 60 marbles need to be added, as  80/100= 
<gadget id="calculator"> 80/100</gadget>
<output>4/5 = around 0.8</output>
0.8 or 80%   choose 60
<result>A</result>
a bag of blue and green colored marbles has 50% green marbles, with a total of 40 marbles. how many green marbles need to be added to bring their percentage in the bag up to 80%?