Multiple choice

Passage

Directions: Read the following information carefully and answer the question that follow: A piggy-bank contains total 18 coins of Re 1, 50 paise and 25 paise. The difference between Re 1 and 50 paise coins is same as difference between 50 paise and 25 paise coins.

If probability of selecting one 50 paise is double the probability of selecting Re. 1 coin then difference between Re 1 and 25 paise coins can be

  1. 6

  2. 8

  3. 9

  4. 10

  5. 11
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let x, y, z be the number of Re 1, 50p, and 25p coins. x+y+z=18. x-y = y-z implies x+z=2y. Substituting into x+y+z=18 gives 3y=18, so y=6. x+z=12. Probability P(50p) = 2*P(Re 1) implies y/18 = 2*(x/18), so y=2x. Since y=6, x=3. Then z=9. Difference between Re 1 and 25p is |3-9| = 6.

AI explanation

Since the probability of selecting a 50 paise coin is double the probability of selecting a Re 1 coin, the number of 50 paise coins is twice the number of Re 1 coins. Letting the counts be x, 2x, and 15 minus 3x for Re 1, 50 paise, and 25 paise coins respectively, the difference between Re 1 and 25 paise coins is (15 minus 3x) minus x, equaling 15 minus 4x. Checking the options, if the difference is 6, then 15 minus 4x equals 6, giving x equals 2, which perfectly satisfies the total coin count of 18.

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