In how many ways can the letters of the word be arranged?
I. The word is LETTER.
II. The word has 6 letters.
I: 6!/(2! 2!) = 180. Sufficient.
II: repeats unknown (PLANET gives 720). Not sufficient.
Permutations and Combinations · Exercise 5 of 5
20 data sufficiency questions on permutations and combinations.
Directions: each question is followed by two statements. Decide whether the data in the statements is sufficient to answer the question, and choose the matching option.
In how many ways can the letters of the word be arranged?
I. The word is LETTER.
II. The word has 6 letters.
I: 6!/(2! 2!) = 180. Sufficient.
II: repeats unknown (PLANET gives 720). Not sufficient.
How many handshakes took place?
I. Each person shook hands once with every other person.
II. There were 10 people and each pair shook hands exactly once.
I: number of people unknown. Not sufficient.
II: 10C2 = 45. Sufficient.
How many sides does the polygon have?
I. It has 20 diagonals.
II. Its interior angles add up to 1,080°.
I: n(n − 3)/2 = 20 → n = 8. Sufficient.
II: (n − 2) × 180 = 1,080 → n = 8. Sufficient.
How many different committees can be formed?
I. Each committee has 3 members chosen from a club.
II. The club has 8 members.
I alone: club size unknown. Not sufficient.
II alone: committee size unknown. Not sufficient.
Together: 8C3 = 56. Sufficient.
In how many ways can the guests sit around a round table?
I. There are at least 5 guests.
II. There are fewer than 8 guests.
Neither fixes the number.
Together: 5, 6 or 7 guests give 24, 120 or 720. Not sufficient.
How many 3-digit numbers can be formed?
I. They use the digits 1 to 5, with no digit repeated.
II. The numbers are odd.
I: 5 × 4 × 3 = 60. Sufficient.
II: the digits allowed are unknown. Not sufficient.
How many triangles can be formed from the points?
I. The points lie in a plane.
II. There are 10 points and no three are collinear.
I: number and arrangement unknown. Not sufficient.
II: 10C3 = 120. Sufficient.
What is the value of n?
I. nC2 = 28.
II. nP2 = 56.
I: n(n − 1)/2 = 28 → n = 8. Sufficient.
II: n(n − 1) = 56 → n = 8. Sufficient.
In how many ways can 2 boys and 2 girls be chosen?
I. There are 5 boys.
II. There are 4 girls.
Each statement gives only one group. Not sufficient.
Together: 5C2 × 4C2 = 60. Sufficient.
How many shortest routes are there from A to B along a street grid?
I. A and B are corners of the same rectangular grid.
II. B is 7 blocks from A by a shortest route.
I gives no sizes. Not sufficient.
II: 7 blocks could be 4 + 3 (35 routes) or 5 + 2 (21). Not sufficient.
Together: still not fixed. Not sufficient.
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