A basket contains 7 red balls and 8 blue balls If 3 balls are picked at random, what is the probability all are red ?
a)3/8
b)1/5
c)3/7
d)1/13
e)none of these

• red balls=7 and blue balls=8
  So total probability=(7+8)c3
  ==>15C3==>(15*14*13)/3*2*1
  ==>35*13
  For all red=7C3==>35
  ie.Probability for all red ball=35/(35*13)=1/13
• 13 years agoHelpfull: Yes(10) No(0)
• 2/5
  
  5 times to draw
  in frst 2 times all 3 balls may be blue.
  3rd time it may be b,r,r.
  so surly it remains for 4th n 5th times
  
• 13 years agoHelpfull: Yes(0) No(5)
• Red Balls = 7
  Blue Balls = 8
  Total No. Of Balls = 7+8= 15
  7c3= 7*6*5/3*2*1=35
  15c3 = 15*14*13/3*2*1= 455
  ==> For Probability of Red Ball= 7c3/15c3
  35/455 = 1/13
  Answer:- 1/13
• 2 years agoHelpfull: Yes(0) No(0)