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Quantitative Aptitude

PERMUTATION AND COMBINATION MCQs

Permutations And Combinations

Total Questions : 444 | Page 41 of 45 pages
Question 401. In how many ways can three consonants and two vowels be selected from the letters of the word “TRIANGLE”?
  1.    25
  2.    13
  3.    40
  4.    30
 Discuss Question
Answer: Option D. -> 30
THE WORD CONTAINS FIVE CONSONANTS. THREE VOWELS, THREE CONSONANTS CAN BE SELECTED FROM FIVE CONSONANTS IN ⁵C₃ WAYS, TWO VOWELS CAN BE SELECTED FROM THREE VOWELS IN ³C₂ WAYS.
3 CONSONANTS AND 2 VOWELS CAN BE SELECTED IN ⁵C₂ . ³C₂ WAYS I.E., 10 * 3 = 30 WAYS.
Question 402. How many four digit even numbers can be formed using the digits {2, 3, 5, 1, 7, 9}
  1.    60
  2.    360
  3.    120
  4.    240
 Discuss Question
Answer: Option A. -> 60
THE GIVEN DIGITS ARE 1, 2, 3, 5, 7, 9
A NUMBER IS EVEN WHEN ITS UNITS DIGIT IS EVEN. OF THE GIVEN DIGITS, TWO IS THE ONLY EVEN DIGIT.
UNITS PLACE IS FILLED WITH ONLY ‘2’ AND THE REMAINING THREE PLACES CAN BE FILLED IN ⁵P₃ WAYS.
NUMBER OF EVEN NUMBERS = ⁵P₃ = 60.
Question 403. How many four digit numbers can be formed using the digits {1, 3, 4, 5, 7,9}(repetition of digits is not allowed)?
  1.    360
  2.    60
  3.    300
  4.    180
 Discuss Question
Answer: Option A. -> 360
THE GIVEN DIGITS ARE SIX.
THE NUMBER OF FOUR DIGIT NUMBERS THAT CAN BE FORMED USING SIX DIGITS IS ⁶P₄ = 6 * 5 * 4 * 3 = 360.
Question 404. A bag contains nine yellow balls, three white balls and four red balls. In how many ways can two balls be drawn from the bag?
  1.    ⁹C₂
  2.    ³C₂
  3.    ¹⁶C₂
  4.    ¹²C₂
 Discuss Question
Answer: Option C. -> ¹⁶C₂
TOTAL NUMBER OF BALLS = 9 + 3 + 4
TWO BALLS CAN BE DRAWN FROM 16 BALLS IN ¹⁶C₂ WAYS.
Question 405. In a class there are 20 boys and 25 girls. In how many ways can a boy and a girl be selected?
  1.    400
  2.    500
  3.    600
  4.    20
 Discuss Question
Answer: Option B. -> 500
WE CAN SELECT ONE BOY FROM 20 BOYS IN 20 WAYS.
WE SELECT ONE GIRL FROM 25 GIRLS IN 25 WAYS
WE SELECT A BOY AND GIRL IN 20 * 25 WAYS I.E., = 500 WAYS.
Question 406. A committee has 5 men and 6 women. What are the number of ways of selecting a group of eight persons?
  1.    165
  2.    185
  3.    205
  4.    225
 Discuss Question
Answer: Option A. -> 165
TOTAL NUMBER OF PERSONS IN THE COMMITTEE = 5 + 6 = 11
NUMBER OF WAYS OF SELECTING GROUP OF EIGHT PERSONS = ¹¹C₈ = ¹¹C₃ = (11 * 10 * 9)/(3 * 2) = 165 WAYS.
Question 407. A letter lock consists of three rings each marked with six different letters. The number of distinct unsuccessful attempts to open the lock is at the most__________?
  1.    216
  2.    243
  3.    215
  4.    729
 Discuss Question
Answer: Option C. -> 215
SINCE EACH RING CONSISTS OF SIX DIFFERENT LETTERS, THE TOTAL NUMBER OF ATTEMPTS POSSIBLE WITH THE THREE RINGS IS = 6 * 6 * 6 = 216. OF THESE ATTEMPTS, ONE OF THEM IS A SUCCESSFUL ATTEMPT.
MAXIMUM NUMBER OF UNSUCCESSFUL ATTEMPTS = 216 – 1 = 215.
Question 408. What are the number of ways to select 3 men and 2 women such that one man and one woman are always selected?
  1.    100
  2.    60
  3.    30
  4.    20
 Discuss Question
Answer: Option C. -> 30
THE NUMBER OF WAYS TO SELECT THREE MEN AND TWO WOMEN SUCH THAT ONE MAN AND ONE WOMAN ARE ALWAYS SELECTED = NUMBER OF WAYS SELECTING TWO MEN AND ONE WOMAN FROM MEN AND FIVE WOMEN
= ⁴C₂ * ⁵C₁ = (4 * 3)/(2 * 1) * 5
= 30 WAYS.
Question 409. A committee has 5 men and 6 women. What are the number of ways of selecting 2 men and 3 women from the given committee?
  1.    150
  2.    200
  3.    250
  4.    300
 Discuss Question
Answer: Option B. -> 200
THE NUMBER OF WAYS TO SELECT TWO MEN AND THREE WOMEN = ⁵C₂ * ⁶C₃
= (5 *4 )/(2 * 1) * (6 * 5 * 4)/(3 * 2)
= 200
Question 410. How many 4-letter words with or without meaning, can be formed out of the letters of the word, ‘LOGARITHMS’, if repetition of letters is not allowed?
  1.    40
  2.    400
  3.    5040
  4.    2520
 Discuss Question
Answer: Option C. -> 5040
NO EXPLANATION IS AVAILABLE FOR THIS QUESTION!

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