The ratio of the no. of white balls in a bag to that of black balls is 1:2. If 9 grey balls are added the ratio of nos. of white, black and grey become 2:4:3. How many black balls were in the bag?

a) 6 b) 9 c) 12 d) 8

• ans. c) 12
  
  if 9 balls are added then the ratio to the combination
  becomes 2:4:3.
  
  9 balls make the ratio 3 for grey balls in tht mixture.
  so the factor is 9/3 = 3 (in tht mixture)
  
  so the same factor has to be maintained through out the
  ratio. so black balls is 4 * 3 = 12 and white balls is 2 *
  3 = 6.
• 12 years agoHelpfull: Yes(15) No(0)
• 3 out of 9 parts are grey balls
  so 3/9 p = 9
  so 1/9 p = 3
  black balls are 4 parts
  so 4/9 = 12
  so nmbr of black balls are 12
• 10 years agoHelpfull: Yes(2) No(0)