Find the total number of balls in the bag
1. 91
2. 84
3. 63
4. none of these
5. cannot be determined
1. 91
2. 84
3. 63
4. none of these
5. cannot be determined
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Correct Answer – Option 3 : 63
Calculation:
Let the number of green balls and blue balls present in the bag be ‘g’ and ‘b’ respectively
Also, number of red balls = 17
Total number of balls = (17 + g + b)
Probability of drawing a red ball = 17/(17 + g + b)
Probability of drawing a green ball = g/(17 + g + b)
Probability of drawing a blue ball = b/(17 + g + b)
Now a/q we have
⇒ g/(17 + g + b) = 1/7 + 17/(17 + g + b)
⇒ (g – 17)/(17 + g + b) = 1/7
⇒ 6g – b = 136 …..(i)
also,
⇒ b/(17 + g + b) = 1/21 + 17/(17 + g + b)
⇒ (b – 17)/(17 + g + b) = 1/21
⇒ 20b – g = 374 …..(ii)
using equation (i) and (ii), we get
g = 26, b = 20
∴ Required total number of balls in the bag = (26 + 20 + 17) = 63