Carcass wrote:
In a certain summer school program, there are five periods in the day. Each student takes English, Math, History, Science, and Science Lab. In how many orders can a student schedule be arranged given that Science lab must immediately follow the Science class?
A. 20
B. 24
C. 100
D. 120
E. 135
Take the Science, and Science Lab classes and
"glue" them together to get the super class "
Science-Science-Lab"
This ensures that Science Lab immediately follows the Science class
So, we now have only 4 classes: English, Math, History and
Science-Science-LabWe can arrange n objects in n! ways.
So, we can arrange these 4 classes in 4! ways (i.e. 24 ways)
Answer: B
Cheers,
Brent