The probability of selecting a blue marble at random from a jar that contains only blue, black and green marbles is 1/5 . The probability of selecting a black marble at random from the same jar is 1/4 . If the jar contains 11 green marbles, find the total number of marbles in the jar.

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Deepak BoraNewbie

Asked: July 26, 20202020-07-26T20:17:05+05:30 2020-07-26T20:17:05+05:30In: CBSE

CBSE 10th Class past year question paper

Year 2019

SET 1, Code Number- 30/2/1

Question number – 9

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Deepak Bora · Answer 1 · 2020-07-28T20:28:48+05:30

Deepak Bora Newbie

This answer was edited.

P(blue marble) = 1/5
P(black marble) = 1/4
∴ P(green marble) = 1 – ( (1/5) + (1/4))

= 11/20
Let total number of marbles be X
then,

(11/20) × X = 11

X = 20