1 pipe can drain a swimming pool in 4 hours. A second pipe can drain the pool in 6 hours. How long will it take to drain the pool if both pipes are used? 3 hours
2 2/5 hours
10 hours
2 hours​

(a) (8%) compute the probability of an even integer among the 100 integers 1! , 2! , 3! , until 100! (here n! is n factorial or n*(n-1)*(n-2) *… 1) (b) (16%) compute the probability of an even integer among the 100 integers: 1, 1+2, 1+2+3, 1+2+3+4, …., 1+2+3+… + 99, and 1+2+3+… + 100

Tom can paint the fence in 12 hours, but if he works together with a friend they can finish the job in 8 hours. how long would it take for his friend to paint this fence alone?

What’s the volume of the triangular prism?