In a shelf there are 3 different Hindi books and 2 different Sanskrit books. A student can select a Hindi Book and a Telugu book in `3xx2=6` ways as explained below.
Let the Hindi books be `H_1,H_2,H_3` and Sanskrit books be `S_1,S_2`.
The six selections are `H_1S_1,H_1S_2,H_2S_1,H_2S_2,H_3S_1,H_3S_2`

If a man has 3 different coloured plants and 3 different coloured shirts. The number of ways that he can select a pair (I,e. one pant and one shirt is 3xx3=9 as explained below. Let the plants be P_1P_2,P_3 and shirts be S_1,S_2,S_3 . He can select a pair from the following P_1S_1,P_1S_2,P_1S_3,P_2S_1,P_2S_2,P_2S_3,P_3S_1,P_3S_1,P_3P_2,P_3P_3 ., 9 ways.

A shelf contains 3 different Hindi books (H_1,H_2,H_3) and 2 different Sanskrit books (S_1,S_2) . The number of ways to select one book of any language either Hindi or sanskrit is (3+2) i.e., ways. The 5 ways are H_1,H_2,H_3,S_1,S_2

There are 7 Telugu books and 4 Hindi books. From those in how many ways can 4 Telugu and 1 Hindi book be arranged so that the Hindi book is always at the middle is

Find the number of ways of selecting 4 English, 3 Telugu and 2 Hindi books out of 7 English, 6 Telugu and 5 Hindi books.

Why the bond angles in H_(2)O & H_(2)S are different ? Give reason.

In the reaction, H_(2)S+H_(2)O_(2) to S+2H_(2)O:

The bond angle in H_2 O is 105^@ but in H_2 S is 92^@ . Explain the difference.