Podcast
Questions and Answers
What is the formula for the number of permutations of n objects taken r at a time?
In how many ways can 4 speakers be arranged in a row for a photo?
How many ways can 5 boys and 4 girls be arranged on a bench if boys and girls are in separate groups?
How many ways can 5 boys and 4 girls be arranged on a bench if Anne and Jim wish to stay together?
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What is the number of ways to arrange 5 objects in a circle?
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How many 4-digit numbers greater than 4000 can be formed from the digits 2, 3, 4, 5, and 6?
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What is the number of ways 6 men and 6 women can sit at a round table if men and women alternate?
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How many 4-digit even numbers can be formed from the digits 2, 3, 4, 5, and 6?
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What is the number of ways 6 men and 6 women can sit at a round table if there are no restrictions?
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How many 5-digit numbers greater than 4000 can be formed from the digits 2, 3, 4, 5, and 6?
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What is the total possible number of hands in a poker game where 5 cards are dealt from a regular pack of 52 cards?
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How many hands of poker have 4 Kings?
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How many ways can 4 Maths books be arranged from 6 different Maths books?
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What is the number of ways to choose 3 Aces and 2 Kings from a deck of 52 cards?
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What is the number of ways to arrange 7 books on a shelf where 4 Maths books are chosen from 6 different Maths books and 3 English books are chosen from 5 different English books, with no restrictions?
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If a bookshelf has 8 shelves and each shelf can hold 5 books, how many ways can the books be arranged on the shelves?
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A die is rolled 4 times. What is the number of possible outcomes?
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A license plate consists of 3 letters and 2 digits. How many possible license plates are there?
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If 5 people are to be arranged in a row, what is the number of possible arrangements?
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If a bag contains 6 balls and 3 balls are drawn at random, what is the number of possible outcomes?
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If a word consists of 4 letters and each letter can be chosen from 26 possible letters, what is the number of possible words?
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If 4 Maths books are selected from 6 different Maths books and 3 English books are chosen from 5 different English books, how many ways can the seven books be arranged on a shelf if a Maths book is at the beginning of the shelf?
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If 4 Maths books are selected from 6 different Maths books and 3 English books are chosen from 5 different English books, how many ways can the seven books be arranged on a shelf if Maths and English books alternate?
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If 4 Maths books are selected from 6 different Maths books and 3 English books are chosen from 5 different English books, how many ways can the seven books be arranged on a shelf if a Maths book is at the beginning and an English book is in the middle of the shelf?
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How many different 8 letter words are possible using the letters of the word SYLLABUS?
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If a word is chosen at random from the letters of the word SYLLABUS, what is the probability that the word contains the two S’s together?
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What is the formula to find the number of ways to arrange the seven books on a shelf if a Maths book is at the beginning of the shelf?
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Study Notes
Permutations and Combinations
- The multiplication rule states that if one event can occur in
m
ways, a second event inn
ways, and a third event inr
ways, then the three events can occur inm × n × r
ways. - Repetition of an event:
- If one event with
n
outcomes occursr
times with repetition allowed, then the number of ordered arrangements isn^r
. - Example: Rolling a die
r
times, the number of arrangements is6^r
.
- If one event with
- Factorial representation:
-
n! = n(n – 1)(n – 2)………..3 × 2 × 1
- Example:
5! = 5 × 4 × 3 × 2 × 1
- Note:
0! = 1
-
- Arrangements or permutations:
- The number of permutations of
n
objects takenr
at a time is given bynPr = n! / (n – r)!
. - Example:
4P4 = 4!
and4P2 = 12
- The number of permutations of
- Permutations with restrictions:
- Example:
5
boys and4
girls can be arranged on a bench in5! × 4!
ways if there are no restrictions. - If boys and girls alternate, the number of arrangements is
5! × 4!
. - If boys and girls are in separate groups, the number of arrangements is
2 × 5! × 4!
. - If
Anne
andJim
wish to stay together, the number of arrangements is2 × 8!
.
- Example:
- Further permutations and combinations:
- Example:
4
Maths books are selected from6
different Maths books, and3
English books are chosen from5
different English books. The number of ways to arrange the7
books on a shelf is6C4 × 5C3 × 7!
. - If a Maths book is at the beginning of the shelf, the number of arrangements is
6 × 5C3 × 5C3 × 6!
. - If Maths and English books alternate, the number of arrangements is
6P4 × 5P3
. - If a Maths book is at the beginning and an English book is in the middle of the shelf, the number of arrangements is
6 × 5 × 5C3 × 4C2 × 5!
.
- Example:
- Circular arrangements:
- The number of ways to arrange
n
objects in a circle is(n – 1)!
. - Example:
6
men and6
women sit at a round table. If there are no restrictions, the number of ways they can sit is11!
. - If men and women alternate, the number of arrangements is
5! × 6!
. - If
Ted
andCarol
must sit together, the number of arrangements is2! × 10!
. - If
Bob
,Ted
, andCarol
must sit together, the number of arrangements is3! × 9!
.
- The number of ways to arrange
- Combinations:
- The number of combinations of
n
objects takenr
at a time is given bynCr = n! / (r! × (n – r)!
). - Example:
52C5
is the total possible number of hands in a game of poker. - Example: The number of hands with
4
Kings isC4 × 48C1
. - Example: The number of hands with
2
Clubs and3
Hearts isC2 × 13C3
.
- The number of combinations of
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Description
Test your understanding of the multiplication rule and repetition of events in permutations and combinations. This quiz is designed for HSC mathematics students revising for their exams.