The first question can be any one of the 10. For each of these . . .
The second question can be any one of the remaining 9. For each of these . . .
The third question can be any one of the remaining 8.
Total number of ways to choose 3 questions = (10 x 9 x 8) = 720 ways.
But the same 3 questions can be chosen in any one of 6 sequences.
So the number of different sets of 3 questions is only 720/6 = 120 .
100,000,000 ways
This is 6! {factorial} = 6 x 5 x 4 x 3 x 2 x 1 = 720. The way this works: take student A, who can choose any of the 6 desks, then for each of those 6 choices that student A makes, student B has 5 desks to choose from, after that choice has been made, student C has 4 desks to choose from, ... until the last student has only one to choose from.
If he must answer the last question, he effectively needs to select 6 from 10. This can be done in 10C6 = 10*9*8*7/(4*3*2*1) = 210 ways.
Nine
210 or 1024 ways.
330 ways. Once we know he must answer the last question, the issue is really one of choosing 4 questions from the first 11 questions on the exam. There are 11 ways to choose the first question, 10 ways to choose the second, 9 ways to choose the third, and 8 ways to choose the fourth, so that would be 11*10*9*8... but the order of the questions doesn't matter. So we divide by the number of ways to rearrange the 4 questions (4*3*2*1=24), to get 330.
they can complete this exam 300 ways
100,000,000 ways
Two books are compulsory, so the student really wants to know how many ways he can pick 3 out of 7. That is 35.
Five (5) multiply by (*) Four (4) = Twenty (20).
16
Combination; number of ways = 21
The first student has 3 chairs to choose from. Once he has mad the choice, the second student has 2 chairs to choose from. And the last student only has 1 choice, so 3 x 2 x 1 = 6 ways.Here are the six ways. For ease, call the students A, B, and C:ABCACBBACBCACABCBA
This is 6! {factorial} = 6 x 5 x 4 x 3 x 2 x 1 = 720. The way this works: take student A, who can choose any of the 6 desks, then for each of those 6 choices that student A makes, student B has 5 desks to choose from, after that choice has been made, student C has 4 desks to choose from, ... until the last student has only one to choose from.
If he must answer the last question, he effectively needs to select 6 from 10. This can be done in 10C6 = 10*9*8*7/(4*3*2*1) = 210 ways.
An essay question can benefit a student in two ways: It can encourage the student to think more clearly, as to express the idea in writing, and hence it can also sharpen the student's writing skills.
144 ways