Basic Maths Grand Test - Q24

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A bag contains 4 Red and 6 Black balls. A ball is drawn at random from the bag, its color is observed and this ball along with two additional balls of the same color are returned to the bag. If now a ball is drawn at random from the bag, then the probability that this drawn ball is red is :

A. 2/5

B. 1/5

C. 3/4

D. 3/10

asked Nov 19 in Basic Maths by gbmentor (85,520 points)
reshown Nov 20 by getgatebook

1 Answer

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Initially-  R-4 & B-6 balls.

1) if red is drawn then probability = 4/10.  Then that red + 2 more red balls are added to bag. So now R- 6 and B-6. Now again 2nd time it is red then probability= 6/12

2) If black is drawn then (From initial R-4 nad B-6) then probability of black = 6/10. Then that drawn black + 2 more black balls are added into bag. Now again 2nd time ball is drawn and it is red, its probability= 4/12 (As R-4 and B-8).


Therefore probability of red drawn = 4/10 * 6/12 + 6/10 * 4/12= 48/120= 2/5.

answered Nov 20 by bhargavakapilpro20 (13,760 points)