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    Question

    A box contains 5 blue jellies, some red jelly and rest

    yellow jelly. The probability of picking a red ball at random is 3/10, while the probability of picking a yellow ball at random is 1/5. Find the total number of jellies in the box.
    A 12 Correct Answer Incorrect Answer
    B 15 Correct Answer Incorrect Answer
    C 18 Correct Answer Incorrect Answer
    D 20 Correct Answer Incorrect Answer
    E 10 Correct Answer Incorrect Answer

    Solution

    Let the number of red jelly and yellow jelly in the box be ‘x’ and ‘y’ respectively. According to the question, {x/(5 + x + y)} = 3/10 Or, 7x – 3y = 15….. (1) Also, {y/(5 + x + y)} = 1/5 Or, 4y – x = 5……. (2) On solving equation (1) and (2), we get x = 3 and y = 2 Therefore, total number of jelly = 5 + x + y = 10

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