From a class of 25 students, 10 are to be chosen for an excursion party there are 3 students who decide that either all of them will join or none of them will join. In how many ways can they be chosen?

Now a day’s teenager’s behavior is highly influenced under peer pressure without considering its pros and cons. Do you think that teachers’ suggestion plays an important role in development of students’ life?

**We have following cases:**

(i) Three particular students join: now we have to choose 7 students from the remaining 22 students

So number of ways = ^{22}C_{7}

(ii) Three particular students do not join. Here we have to choose 10 students from remaining 22 students

So number of ways = ^{22}C_{10}

Hence, total number of ways = ^{22}C_{7}+ ^{22}C_{10} = 817190

Teachers’ suggestion plays a very important role in development of students’ life. They mould the students to bring out their skills or improvise them, teach good habits/attitudes and help them to become good citizens of the nation.