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MODERN MATHS MCQs

Total Questions : 95 | Page 7 of 10 pages
Question 61.


For a drama, 3 students need to be selected out of 6 students A,B,C,D,E and F. If A is already selected, what is the probability of selecting C also?


  1.     0.5
  2.     0.2
  3.     0.3
  4.     0.4
 Discuss Question
Answer: Option D. -> 0.4
:
D

If A is selected, then two more students need to be selected. This can be done in 5C2 ways= 10


If C is also selected, only one more out of the remaining 4 needs to be selected.
That can be done in 4 ways.
Thus, Probability =410 = 0.4


Question 62.


If 30% of the visitors to an ice cream shop have chocolate ice-cream, then what is the probability that 2 out of 3 people who entered the store on Saturday at 5 pm will have chocolate ice-cream?


  1.     0.16
  2.     0.15
  3.     0.19
  4.     0.28
 Discuss Question
Answer: Option C. -> 0.19
:
C

Probability of a success= 0.3


Probability of a failure= 0.7


Required Probability = 0.3 × 0.3 × 0.7 × 3C1 = 0.189


Question 63.


What is the probability of getting at least one six in a single throw of three unbiased dice?


  1.     16
  2.     125216
  3.     136
  4.     91216
 Discuss Question
Answer: Option D. -> 91216
:
D

 


The probability of getting no six is (56)3 = 125216


Hence the probability of getting at least one six is 1 - 12521691216


Question 64.


A Number is selected at random from first thirty natural numbers. What is the chance that it is a multiple of either 3 or 13?


  1.     1730
  2.     25
  3.     1130
  4.     415
 Discuss Question
Answer: Option B. -> 25
:
B

Total sample space is 30


The number of multiples of 3 are 10 and the number of multiples of 13 are 2, out of which none of them are common.
Hence, answer is 25


Question 65.


4 out of 15 apples are rotten. They are taken out one by one at random and examined. The ones which are examined are not replaced. What is the probability that the 9th one examined is the last rotten one?


  1.     4C3×11C515C3 × 17C1
  2.     11C5×4C415C9
  3.     4C3×11C515C9
  4.     None of these
 Discuss Question
Answer: Option A. -> 4C3×11C515C3 × 17C1
:
A

 Lets consider upto the 9th apple. The first 8 apples should have 3 rotten ones and remaining 5 good ones. This can be chosen in 4C3 × 11C5 ways.
Total number of selections of 8 apples out of 15 apples is 15C8 .
The last apple is the only rotten one left, which can be selected in 1 way.
Total number of ways of selecting that 1 apple from remaining 15 – 8 = 7 apples = 7C1 ways


Total probability = 4C3×11C515C3 × 17C1


Question 66.


What is the probability that a two digit number selected at random will be a multiple of '3' and not a multiple of '5'?


  1.     215
  2.     415
  3.     115
  4.     310
 Discuss Question
Answer: Option B. -> 415
:
B

Sample space is 90 numbers, of which , 903 = 30 are multiples of 3. 905= 18 are multiples of 5, of which every 1 out of 3 are multiples of both 3 and 5.


Probability that a two-digit number is a multiple of 3 and not a multiple of 5 = 30-6 = 2490= 415


Question 67.


When two dice are thrown simultaneously, what is the probability that the sum of the two numbers that turn up is less or equal to 10?


  1.     56
  2.     1112
  3.     16
  4.     112
 Discuss Question
Answer: Option B. -> 1112
:
B

First find the probability of sum being greater than 10. Combination whose sum of 12 is (6, 6)


Combinations whose sum of 11 is (5, 6), (6, 5).


Therefore, there are totally 3 occurrences out of 36 occurrences that go against the given condition.


Probability whose sum of two numbers is greater than or equal to 11 = 336 = 112.


Hence probability whose sum of two numbers is lesser than 11 = 1 – 1121112 .


 


Question 68.


A furniture shop has six identical steel cabinets of brand A and four identical steel cabinets of brand B. Three customers buy one cabinet each. Then the probability that two or more cabinets of brand A have been sold


  1.     13
  2.     23
  3.     12
  4.     34
 Discuss Question
Answer: Option C. -> 12
:
C

 


The total possibilities are 2 × 2 × 2 = 8 (each customer has two possibilities).
These are AAA, AAB, ABA, BAA, BBA, BAB, ABB, BBB.
The favourable outcomes are only 4 (AAA, AAB, ABA, BAA).
Thus the probability = 48
 = 12 .


Question 69.


Two dice are thrown simultaneously. The probability of getting an even number on both the dice is?


  1.     12
  2.     34
  3.     14
  4.     15
 Discuss Question
Answer: Option C. -> 14
:
C

Probability of getting an even number of the first dice and the second dice is= 36 × 36 = 14.


 


Question 70.


Arpit and Rita will play one game of Rock, Paper, Scissors. In this game, each will select and show a hand sign for one of the three items. Rock beats Scissors, Scissors beat Paper, and Paper beats Rock. Assuming that both Arpit and Rita have an equal chance of choosing any one of the hand signs, what is the probability that Arpit will win?


  1.     56
  2.     23
  3.     12
  4.     13
 Discuss Question
Answer: Option D. -> 13
:
D

 No matter what sign Arpit throws, there is one sign Rita could throw that would beat it, one that would tie, and one that would lose. Rita is equally likely to throw any one of the three signs. Therefore, the Probability that Arpit will win is 13


Probability that Rita will win = 13


Probability of a tie = 13.


Probability that Arpit will win = 13 


The correct answer is (d). 


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