Why do Stars Twinkle? for students | Class 9 & 10

Stars are twinkling due to

How does refraction take place in the atmosphere? Why do stars twinkle but not the planets?

In class 12 there are 8 students. In class 11 there are 6 students .In class 10 there are 5 students . Total ways of selecting 10 students , such that there are at least 2 students from each class and at most 5 students from 11 students of Class 10 and 11 combined is 100k. Then find value of k

Direction: There are 1250 total students in 5 different classes in a school. The number of students in class I is 50 less than the number of students in class II. The number of class IV students is 50 more than the number of students in class II. The average number of students in class III and class V is 250. The number of students in class III is 10% less than the number of students in class I. The ratio of the total number of students of class V to the total number of students of class III is