Mathematics
A box contains some black balls and 30 white balls. If the probability of drawing a black ball is two-fifths of a white ball; find the number of black balls in the box.
Related Questions
Two dice are thrown simultaneously. What is the probability that :
(i) 4 will not come up either time ?
(ii) 4 will come up at least once ?
Offices in Delhi are open for five days in a week (Monday to Friday). Two employees of an office remain absent for one day in the same particular week. Find the probability that they remain absent on :
(i) the same day
(ii) consecutive day
(iii) different days.
From a pack of 52 playing cards, all cards whose numbers are multiples of 3 are removed. A card is now drawn at random. What is the probability that the card drawn is
(i) a face card (King, Jack or Queen)
(ii) an even numbered red card ?