An experiment succeeds twice as often as it fails. What is the probability that in the next 5 trials there will be four successes?

The length of a ladder is exactly equal to the height of the wall it is resting against. Iflower end of the ladder is kept on a stool of height 3 m and the stool is kept 9 m awayfrom the wall, the upper end of the ladder coincides with the top of the wall. Then,the height of the wall is:

The cost of painting the walls of a hall 30 meters long, 20 meters broad and 12 meters high, if it costs 25 paise per sq. metre