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
(i) 2 girls (ii) 1 girl (iii) No girl
Also check whether the sum of these probabilities is 1.
An organization selected 2400 families at random and surveyed them to determine a relationship between income level and the number of vehicles in a family. The information gathered is listed in the table below:-
|Vehicles per family|
|Less than 7000||10||160||25||0|
|7000 – 10000||0||305||27||2|
|10000 – 13000||1||535||29||1|
|13000 – 16000||2||469||59||25|
|16000 or more||1||579||82||88|
Suppose a family is chosen, find the probability that the family chosen is
(i) earning Rs 10000 − 13000 per month and owning exactly 2 vehicles.
(ii) earning Rs 16000 or more per month and owning exactly 1 vehicle.
(iii) earning less than Rs 7000 per month and does not own any vehicle.
(iv) earning Rs 13000 − 16000 per month and owning more than 2 vehicles.
(v) owning not more than 1 vehicle.
A teacher wanted to analyse the performance of two sections of students in a mathematics test of 100 marks. Looking at their performances, she found that a few students got under 20 marks and a few got 70 marks or above. So she decided to group them into intervals of varying sizes as follows: 0 − 20, 20 − 30… 60 − 70, 70 − 100. Then she formed the following table:-
|Marks||Number of students|
|0 - 20||7|
|20 - 30||10|
|30 - 40||10|
|40 - 50||20|
|50 - 60||20|
|60 - 70||15|
|70 - above||8|
(i) Find the probability that a student obtained less than 20 % in the mathematics test.
(ii) Find the probability that a student obtained marks 60 or above.
In a particular section of Class IX, 40 students were asked about the months of their birth and the following graph was prepared for the data so obtained:-
Find the probability that a student of the class was born in August.
Eleven bags of wheat flour, each marked 5 kg, actually contained the following weights of flour (in kg):- 4.97, 5.05, 5.08, 5.03, 5.00, 5.06, 5.08, 4.98, 5.04, 5.07, 5.00
Find the probability that any of these bags chosen at random contains more than 5 kg of flour.
- Mathematics Textbook for Class 9