Answer:
80 minutes
Step-by-step explanation:
Rate and Time are inverses of each other
First,
Elise Time = 12
and
Katherine Time = 2 * 12 = 24
Their rates would be (inverses):
Elise Rate = 1/12
Katherine Rate = 1/24
Together their rate is 1/12 + 1/24 = 3/24
Now, the inverse of this rate would be the time it takes to complete 1 bag together, that is:
(3/24) ^ -1 = 24/3 = 8 minutes
So, 10 bags would take them:
8 * 10 = 80 minutes