Introduction to Mathematical Modelling

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Question
CBSEENMA9003987

In a cricket match, a batswoman hits a boundary 6 times out of 30 balls she plays. Find the probability that she did not hit a boundary.

Solution

Let E be the event of hitting the boundary.

Then,
straight P left parenthesis straight E right parenthesis equals fraction numerator his space the space boundary over denominator Total end fraction equals 6 over 30 equals 1 half equals 0.2

∴ Probability of not hitting the boundary
= 1 – Probability of hitting the boundary
= 1 – P(E) = 1 – 0.2 = 0.8.


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Question
CBSEENMA9003988

1500 families with 2 children were selected randomly, and the following data were recorded:

Number of girls in a family

2

1

0

Number of families

475

814

211

Compute the probability of a family, chosen at random, having

(0 2 girls (ii) 1 girl (iii) No girl.

Also check whether the sum of these probabilities is 1.

Solution

Total number of families
= 475 + 814 + 211 = 1500
(i) Probability of a family, chosen at random,
having 2 girls = 475 over 1500 equals 19 over 60
(ii) Probability of a family, chosen at random,
having 1 girl  equals 814 over 1500 equals 407 over 750
(iii) Probability of a family, chosen at random,
having no girl  equals 211 over 1500
Sum of these probabilities
equals 19 over 60 plus 407 over 750 plus 211 over 1500
equals fraction numerator 475 plus 814 plus 211 over denominator 1500 end fraction equals 1500 over 1500 equals 1
Hence, the sum is checked.

Question
CBSEENMA9003989

In a particular section of Class IX, 40 students were asked about the months of their birth, the following graph was prepared for the data so obtained. Find the probability that a student of the class was bom in August.


Solution

Total number of students bom in the year =3+4+2+2+5+1+2+6+3+4+4+4=40
Number of students bom in August = 6
∴ Probability that a student of the class was
born in August = 6 over 40 equals 3 over 20.

Question
CBSEENMA9003990

Three coins are tossed simultaneously 200 times with the following frequencies of different outcomes:

Outcome

3 heads

2 heads

1 head

No head

Frequency

23

72

71

28

If the three coins are simultaneously tossed again, compute the probability of 2 heads coming up.

Solution

Total number of times the three coins are tossed = 200
Number of times when 2 heads appear = 72
∴ Probability of 2 heads coming up
equals 72 over 200 equals 9 over 25.