|
Question 324911: how many 3 person groups can be formed in a club with 8 people?
daria can wash and detail 3 cars in 2 hours. Larry can wash and detail the same 3 cars in 1.5 hours. About how long will it take to wash and detail the 3 cars if they worked together?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! how many 3 person groups can be formed in a club with 8 people?
The 1st chosen is 1 of 8, then 1 of 7, then 1 of 6 --> 8*7*6
But, since ABC is the same as CAB and CBA, you have to divide by 3*2*1
8*7*6/(3*2*1) = 56
--------------------
daria can wash and detail 3 cars in 2 hours. Larry can wash and detail the same 3 cars in 1.5 hours. About how long will it take to wash and detail the 3 cars if they worked together?
The tasks are the same.
Daria does 1/2 of the task per hour.
Larry does 1/1.5 per hour.
Together, they to 1/2 + 1/1.5 = 7/6 per hour
--> 6/7 hours per task
-------------------------
If it's a timed test, use the shortcut product/sum
2*1.5/(2+1.5) = 3/3.5
= 6/7 hours
|
|
|
| |
