6.
In a class, there are 60% boys. Out of the total girls,
30% have blue eyes. If the number of girls having
eyes not of blue colour is 56, What is the total
number of students in the class?
Answers
Answer:
hope,by seeing one of them will help you
Step-by-step explanation:
Exercise 2
In a class in which all students practice at least one sport, 60% of students play soccer or basketball and 10% practice both sports. If there is also 60% that do not play soccer, calculate the probability that a student chosen at random from the class:
1 Plays soccer only.
2Plays basketball only.
3Plays only one of the sports.
4Plays neither soccer nor basketball.
Exercise 3
In a city, 40% of the population have brown hair, 25% have brown eyes and 15% have both brown hair and eyes. A person is chosen at random.
1 If they have brown hair, what is the probability that they also have brown eyes?
2If they have brown eyes, what is the probability of them not having brown hair?
3What is the probability of them having neither brown hair nor brown eyes?
Exercise 4
In a classroom there are 100 pupils, of whom 40 are boys, 30 wear glasses, and 15 are boys who wear glasses. If one student from the class is randomly selected:
1 What is the probability that the student will be a girl who does not wear glasses?
2If we know that the student selected does not wear glasses, what probability that it will be a boy?
Exercise 5
There are two boxes. Box A contains 6 red balls and 4 blue balls and Box B contains 4 red balls and 8 blue balls. A die is rolled, if the number is less than 3, a ball is selected from box A. If the result is 3 or more, a ball is selected from Box B. Calculate:
1 The probability that the ball will be red and selected from Box B.
2The probability that the ball will be blue.
Exercise 6
In order to write an exam, a student needs an alarm clock to wake up, which has proven to successfully wake him 80% of the time. If he hears the alarm in the morning the probability of writing the test is 0.9 and if he doesn´t hear the alarm the probability is 0.5.
1 If he writes the test what is the probability that he heard the alarm clock?
2If he doesn´t write the test: what is the probability that he didn´t hear the alarm clock?
Exercise 7
On a shelf there are 60 novels and 20 poetry books. Person A chooses a book at random off the shelf and leaves with it. Shortly after, Person B chooses another book at random. Calculate:
1 The probability that the book selected by Person B is a novel?
2If it is known that Person B chose a novel: what is the probability that the book selected by Person A was a poetry book?
Exercise 8
It is determined that 25 of every 100 men and 600 of every 1,000 women wear glasses. If the number of women in a particular room is four times more than that of men, calculate the probability of:
1 A person without glasses being randomly selected.
2A woman with glasses being randomly selected.
Answer:
200
Step-by-step explanation:
Given:-
- no. of girls having eyes not of blue color=56 = 70% of total girls
- no. of girls having eye color blue =30% of total girls = 24
- boys in classroom :- 60%
girls in classroom :- 100-60 = 40%
- 10% of girls :- 56÷7 = 8
sol:-
- total no. of girls = no. of girls not having eye color blue +no. of having eye color blue.
= 56 + 24
= 80
- total no .of girls = 80
so,
girls are 40%= 80
then,
10% of total students = 80/2 = 20
so,
boys are 60% = 60×2 = 120
- therefore total no. of students = total no of girls + total no of boys = 80 + 120 = 200