a bag contains 5 red balls and some blue balls . if the probability of drawing a blue ball is double that of red ball, determine the number of blue ball in the bag

LET THE NO. OF BLUE BALLS BE X

NO. OF RED BALLS = 5

TOTAL NO. OF BALLS = NO. OF BLUE BALLS + NO. OF RED BALLS

= X + 5

PROBABILITY OF GETTING BLUE BALL = X / X + 5

PROBABILITY OF GETTING RED BALL = 5/ X +5

ACCORDING TO THE QUESTION,

X / X + 5 = 2 * 5 / X + 5

CANCELLING X+5 FROM BOTH TERMS AS THEY ARE COMMON

X = 10

SO, THERE ARE 10 BLUE BALLS IN THE BAG

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