Answer: it will take them 8.89 hours
Step-by-step explanation:
Amber can paint a room in 20 hours. This means that Amber's working rate per hour is 1/20
Christy can paint the same room in 16 hours. This means that Christy's working rate per hour is 1/16
If they work together, they would be working simultaneously and their unit rates is additive. This means that their combined rate would be
1/20 + 1/16
Assuming it takes t hours for both of them to paint the room working together. It means that their combined working rate per hour is 1/t. Therefore
1/20 + 1/16 = 1/t
(16 + 20/320 = 1/t
36/320 = 1/t
t = 320/36
t = 8.89 hours
Answer:
the answers are B,C,D
a) A n (B' n C') = {3, 9}.
b) (AUB) n (BUC) = {2,4,5,6,7,8}
a) Rewriting C ; C = {4,5,6,7,8}
B' = {3,5,7,9} and C' = {2, 3, 9}
so (B' n C') = {3, 9}
and A n (B' n C') = {3, 9}.
b) {A U B} = { 2,3,4,5,6,7,8,9} and {B U C} = {2,4,5,6,7,8}
so (AUB) n (BUC) = {2,4,5,6,7,8}
