18. The number of ways of selecting “r” objects selected from “n” objects is ref

Question

18. The number of ways of selecting “r” objects selected from “n” objects is referred to as?   

A. Permutations

B. Combinations

C. n factorial

D. none of the above

19. The number of ways of selecting “r” objects selected from “n” objects, where the order of selection is significant is referred to as?

A. Permutations
B. Combinations
C. n factorial
D. None of the above

20. The number of permutations is larger than the number of combinations by what amount?

A. n!

B. (n-r)

C. r!

D. none of the above

21. The number of combinations of 5 items taken 3 at a time = __________.

A. 20

B. 15

C. 10

D. 60

Explanation / Answer

18.

As we just select and not reorder, it is just:

OPTION B: COMBINATIONS

19. As we now order, it is now:

OPTION A: PERMUTATIONS

20.

As we reorder the r objects taken, it is larger by

OPTION C: r!

21.

As nCr = n!/[r!(n - r)/!]

Thus,

5C3 = 10 [OPTION C]

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