In a class of 25 students with roll numbers 1 to 25, a student is picked up at random to answer a question. Find the probability that the roll number of the Selected student is either a multiple of 5 or of 7.

Marks obtained by 2500 students are shown in the following table: A student is selected at random. Find the probability that : he scores more than 80% marks.

Marks obtained by 2500 students are shown in the following table: A student is selected at random. Find the probability that : he scores less than 60% marks.

In a cer tain college, 4% of boys and 1% of girls are taller than 1.75 metres. Furthermore, 60% of the students in the college are girls. A student is selected at random from the college and is found to be taller than 1.75 metres. Find the probability that the selected student is girl.

In a class having 60% boys, 5% of the boys and 10% of the girls have an I.Q. of more than 150. A student is selected at random and found to have an I.Q. of more than 150. Find the probability that the selected student is a boy.

A class consists of 10 boys and 8 girls. Three students are selected at random. Find the probability that the selected group has : all Boys.

Tickets are numbered from 1 to 100. One ticket is picked up at random. Find the probability that the ticket picked up has a number, which is divisible by 5 or 8.

In Class XI of a school 40% of the students study Mathematics and 30% study Biology. 10% of the class study both Mathematics and Biology. If a student is selected at random from the class, find the probability that he will be studying Mathematics or Biology.

In class XI of a school 40% of the students study Mathematics and 30% study Biology 10% of the class study both Mathematics and Biology. If a student is selected at random from the class, find the probability that he will be studying Mathematics or Biology.

A class consists of 10 boys and 8 girls. Three students are selected at random. Find the probability that the selected group has : all girls.