Question 451726: 1.
A teacher has a set of 12 problems to use on a math exam. The teacher makes different versions of the exam by putting 10 questions on each exam. How many different exams can the teacher make?
2.
If 100 C2 has a value of 4,950, what is the value of 100 C98?
Answer by Edwin McCravy(20055)   (Show Source):
You can put this solution on YOUR website!
1.
A teacher has a set of 12 problems to use on a math exam.
The teacher makes different versions of the exam by putting
10 questions on each exam. How many different exams can the
teacher make?
You can either look at it that the teacher has 12 and chooses
10 to put on the exam:
12 C 10 = 66
or you can look at it that she has 12 and chooses 2 to
leave off the exam.:
12 C 2 = 66
[Now if the teacher considers it to be a different test if
he/she lists the same problems in a different order, then
the number of would be 12 P 10 = 239,500,800]
2.
If 100 C 2 has a value of 4,950, what is the value of 100 C 98?
The same value, 4,950. That's because every time you choose
2 from 100 you leave 98 behind.
It's always true that n C r = n C (n-r)
Edwin
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