Can you arrange four 9's and use at most 2 math symbols, to make the total 100?

There are seven sisters in a house in a village where there is no electricity or any gadget.

Sister-1: Reading Novel
Sister-2: Cooking
Sister-3: Playing Chess
Sister-4: Playing Sudoku
Sister-5: Washing clothes
Sister-6: Gardening

what is Sister-7 doing ?

What do you get if you add 2 to 100 four times?

Two trains start at the same time, one from Bangalore to Mysore and the other from Mysore to Bangalore. if they arrive at their destinations one hour and four hours respectively after passing one another, how much faster is one train running than the other?

What goes up but never comes down?

How many bananas can you eat if your stomach is empty?

What is the fewest number of coins that would be required in order to make sure each and every coin touches exactly three other coins?

Irene killed hundreds of people mercilessly and yet the police were not able to put her behind the bars. Why?

I am dry when I go inside, but wet when I am pulled outside.
The longer I am inside, the stronger I get
When I am completely out, I am wet and I literally sag
Who am I?

When I get multiplied by any number, the sum of the figures in the product is always me. What am I?