A bag contains 4 red and 5 yellow balls and 3 are successively drawn out and not replaced What rsquo...........

Quantitative Aptitude (CDS) Probability

A bag contains 4 red and 5 yellow balls, and 3 are successively drawn out and not replaced. What’s the chance of getting different colours alternatively?

5/42

10/63

35/126

1/126

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Explanation:

Total number of balls = 9
Let the first drawn ball is red, so required probability
=4/9×5/8×3/7
=5/42
But here we had started with a red ball. When we start with a yellow ball, the required probability
=5/9×4/8×4/7
=10/63
Since these two cases are mutually exclusive.
Total probability = 5/42 + 10/63
=( 15 + 20 )/126
=35/126