Selecting at least 3 black balls from a set of 6 black balls in total selection of 5 balls can be 3 black and 2 white balls 4 black and 1 white balls 5 black and 0 white balls Therefore, our solution expression looks 6C3 × 3C2 + 6C4 × 3C1 + 6C5 × 3C0 = 20 × 3 + 15 × 3 + 6 × 1 = 60 + 45 + 6 = 111 ways
Pipes ‘A’ and ‘B’ can fill a tank in 6 hours and 9 hours, respectively. If pipe ‘C’ is opened along with pipes ‘A’ and ‘B’, then the...
Pipe ‘A’ can fill a tank in 30 hours while pipe ‘B’ can empty it in 40 hours. They were operated on alternate hours starting with pipe ‘A’. ...
Pipe ‘A’ can fill a tank in 40 hours whereas leak ‘A’ can empty it in 50 hours. If they both operate along with pipe ‘B’, then the given tan...
Pipe ‘A’ and pipe ‘B’ can fill a cistern in 15 minutes and 36 minutes respectively. Pipe ‘C’ alone can empty the cistern in 12 minutes. If a...
Pipe ‘A’ can fill a tank in 15 hours while pipe ‘B’ can empty it in 45 hours. They were operated on alternate hours starting with pipe ‘A’. ...
Pipe ‘A’ can fill a tank in 25 hours while pipe ‘B’ can empty it in 30 hours. They were operated on alternate hours starting with pipe ‘A’. ...
Pipe ‘A’ and pipe ‘B’, together can fill 20% of a tank in 6 hours while pipe ‘C’ takes 36 hours to empty it. ...
Pipe ‘A’ can fill a tank in 20 hours while pipe ‘B’ takes 32 hours to empty it. Pipe ‘A’ is opened alone when the tank was empty and after 1...
Two pipes can fill a tank in 12 and 10 minutes respectively. A waste pipe is used to empty the tank. All three pipes working together can fill the tank ...
P, Q and R three pipes connected to a tank. P and Q together fill the tank in 30 hours, Q and R together fill the tank in 40 hours. P and R together fil...
