Nine friends decide to go for a picnic in two groups. One group decides to go by car and the other group decides to go by train. Find the number of different ways of doing so if there must be at least 3 friends in each group.

30 objects are to be divided in three groups containing 7,10,13 objects. Find the number of distinct ways for doing so.

In a group of 15 boys there are 6 scouts. In how many ways can 8 boys be selected so as to include at least 3 scouts?

Go through the Modern periodic table (fig2.1) and write the names one below the other of the elements of group 1.

In the modern periodic table, the elements are arranged in the increasing order of their atomic number. This arrangement is based on the modern periodic law, which states that the properties of elements are a periodic function of their atomic numbers. In the modern periodic table, each column is called a group and each row is called a period. Elements within the same group show similarity and gradation in properties. This is due to the same number of electroms in the outermost shell . Based on the above paragraph, answer the following question: What is the trend in the variation of valency while going down a group?

While going from Mumbai to Pune by car, the probability that a person will be stopped by each of the 3 policemen who control the traffic at three different places is 0.6. What is the probability that :at least two policeman will stop the person?

Go through the Modern periodic table (fig2.1) and write the names one below the other of the elements of group 1. How many valence electrons are there in each of these elements ?

While going from Mumbai to Pune by car, the probability that a person will be stopped by each of the 3 policemen who control the traffic at three different places is 0.6. What is the probability that :exactly two policeman will stop the person?

Go through the Modern periodic table (fig2.1) and write the names one below the other of the elements of group 1. What similarity do you find in their electronic configuration?

The number of ways in which 10 persons can go in two boats so that there may be 5 on each boat, supposing that two particular persons will not go in the same boat is