Three socks are hung on a line. Two socks are the same and one is different. How many different ways can the socks be arranged?

In this question, it is given that

Harish tthought of a two digit odd number greater than 50. One of its digits was half the other.

Since it is a two digit odd number. So for the number on one's place, we have 5 options which are 1,3,5,7,9. And none of these can be double .

And in the ten's place, it have to be greater then 5. So we have two options, 6 and 8.

And double of 3 is 6, so the number is 63.