Out of a collection of only blue and pink marbles, 2 pink marbles are removed away. After that there are 2 blue marbles for every pink marble. Next, 36 blue marbles are removed away. As a result, there are 5 pink marbles for every blue marble. How many blue marbles are there at present?
Let the number of blue marbles at present be x. The number of pink marbles at present are 5x. If we put back 36 blue marbles, the equation becomes x + 36 = 2 × 5x, which gives 9x = 36, or x = 4 marbles. Note: some information in the question is never used, it is given for confusing the candidate.