5) how hard do these machines work?

ern5231 wrote:Two machines A and B drain water from a tank. A worked alone for 4 hours to
Drain half of the water in the tank. Then, B joined and the remaining water could be drained in 3 hours. In how many hours could B drain the water alone?


I picked up this question from net. Don't have the options. I worked out the answer 24. Wts your opinion?

ern5231 wrote:Two machines A and B drain water from a tank. A worked alone for 4 hours to
Drain half of the water in the tank. Then, B joined and the remaining water could be drained in 3 hours. In how many hours could B drain the water alone?


I picked up this question from net. Don't have the options. I worked out the answer 24. Wts your opinion?

ern5231 wrote:Two machines A and B drain water from a tank. A worked alone for 4 hours to
Drain half of the water in the tank. Then, B joined and the remaining water could be drained in 3 hours. In how many hours could B drain the water alone?


I picked up this question from net. Don't have the options. I worked out the answer 24. Wts your opinion?