Answer:
19 mins
Step-by-step explanation:
Adding up timing od pipe A,B ,C
Answer: 4(x + 4)(x - 4)
Step-by-step explanation:
Answer: C. 
Step-by-step explanation:
Given: Box contains 8 green balls and 4 purple balls.
Total balls = 8+4 = 12
event 1 = first picking green ball
event 2 = second picking purple balls.
As first ball was replaced, that means both events are independent.
Probability that you have selected a green ball and then a purple ball = P(purple ball )
Formula for probability = 
Probability of selecting a purple ball (second pick)= 

The required probability
, so C is correct option.
START WITH 1 COUNT BY ONES 1, 2, 3, 4, 5, 6
START WITH 8 COUNT BY ONES 8, 9, 10, 11, 12, 13