+52 Miss Morrison has a test bank of multiple choice questions. 15 questions are combinations, and 12 are premutations. Miss Morrison is writing a test with 12 multiple choice questions. (Please include steps)
a) How many different tests can she write if she wants to choose 7 combination and 5 premutation multiple choice questions.
b) After she has choosen the 12 questions, in how many orders can she put them on the test?
+129852 Think of it as a job that consists of two parts, A and B
If there are "x" ways to do A and "y" ways to do B, then the total number of ways of doing the whole job is just x * y
So..our job is to choose 12 test questions....And "A" is to choose 7 from 15 combo questions and "B" is to choose 5 from 12 permute questions.
So...the total ways to perform the job is just the number of ways to do A times the total ways to do B = C(15,7) * C(12, 5)
Does that make sense?? {This is known as the Fundamental Counting Principle}
+129852 Hey...are you trying to start a fight on here??? LOL!!!
OK..the number of tests is given by choosing any 7 of the 15 combination questions and choosing any 5 of the 12 permute questions...so we have
C(15,7) * C(12,5) = 5,096,520 different tests ...that's quite a few more than we might expect!!
And the number of orders she can put them in is just 12! = 479,001,600...that's really more than we might expect....!!!
+52 Hahah i feel like these probablility questions are tricky, but I mean no harm 
. Why do we have to multiply the combinations? Dont we add them together? Thanks!
+129852 Think of it as a job that consists of two parts, A and B
If there are "x" ways to do A and "y" ways to do B, then the total number of ways of doing the whole job is just x * y
So..our job is to choose 12 test questions....And "A" is to choose 7 from 15 combo questions and "B" is to choose 5 from 12 permute questions.
So...the total ways to perform the job is just the number of ways to do A times the total ways to do B = C(15,7) * C(12, 5)
Does that make sense?? {This is known as the Fundamental Counting Principle}
+52 Ohh so we are using the product rule rather than rule of sum. The crazy numbers throw me off Thanks!
