Answer:

cold water tap can fill a bath in 3 min

so , in one minute it fills = 1/3 bathtub

hot water tap can fill a bath in 4 min

so in one minute it fills = 1/4 bathtub

waste pipe can empty bathtub in 6 min

so in one minute it empty = 1/6 bathtub

all together makes work in one minute = 1/3 + 1/4 - 1/6

= 4/12 + 3/12 - 2/12

= 5 / 12

so it takes , 12/5 minutes

= 2.4 minutes

i. e. 2 minutes 24 seconds

Step-by-step explanation: