Which country gets ill every time?

If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

Find the next number in the series below

21 32 54 87 131 ?

What part of the chicken has the most feathers?

What building has the most stories?

Make eight squares by moving only two matchsticks.
Note- Square can be of different sizes.

What have one eye but still cannot see?

In the Thar desert, 3 men found a big 24L Jar is full of water. Since there is a shortage of water so they decided to distribute the water among themselves such that they all have equal amounts of it. But they only have a 13L, a 5L and an 11-litre Jar.

How do they do it?

I am the black child of a white father, a wingless bird, flying even to the clouds of heaven. I give birth to tears of mourning in pupils that meet me, even though there is no cause for grief, and at once on my birth, I am dissolved into air. What am I?

A famous swimmer can swim downstream in a lake in exactly 40 minutes with the lake current.
He can swim upstream in that lake in exactly 60 minutes against the lake current.
The length of the lake is 2 km.

How long he can cover the distance of one side at a still lake with no current?