Question

A multiple choice test contains 10 questions. There are four possible answers for
each question.
(a) How many ways can a student complete the test if every question must be
answered?
(b) How many ways can a student complete the test if questions can be left unan-
swered?

Answer 1

Is a 10 choose 4, and b 10 choose 5?

Answer 2

Yeah, that's correct

Answer 3

Did you find the no. of ways?

Answer 4

10 factorial / 10 - 4 factorial?

Answer 5

Oops that's not right. I'll explain you:)

Answer 6

10*9*8*7*6*5?

Answer 7

For the first part, how many ways are there to answer each question?

Answer 8

four

Answer 9

good, so I can answer first question in 4 ways, second also in 4 ways, third also in 4 ways and so on.
Do you get any ideas now?

Answer 10

@tim93 what do you think?

Answer 11

4^10?

Answer 12

are the answers 4^10 and 5^10

Answer 13

Great:D
good work:D

Answer 14

so @tim93 tell me the no. of ways for the second ?

Answer 15

(5^10-1) if at least one must be answered

Answer 16

Thanks @matricked

Answer 17

awesome!

Answer 18

mention not ..