A bag has 10 blue balls and 15 black balls. How many black balls must be removed from the bag so that 50 percent of the balls in the bag shall be black?	Choose the correct choice from the following answers.
A) 1	B) 2	C) 3	D) 4	E) 5
Suppose x black balls need to be removed from the bag.   After x black balls are removed, the bag shall have (15 - x) black balls and the same 10 blue balls; and the total number of balls shall be (15-x) + 10 = 25 - x   Now we want the 50 percent of balls in the bag to be black.   This means 50 percent of (25 - x) should be equal to the number of black balls which is (15 - x).   This means,   50 % of (25 - x) = (15 - x)   Solving above equation we get x = 5.   Ans 5
<result>E</result>
A bag has 10 blue balls and 15 black balls. How many black balls must be removed from the bag so that 50 percent of the balls in the bag shall be black?