Why do we preferably have round manhole covers and not square ones?

Can you find out the total number of triangles in the given figure?

Buy me, smell me or deliver me, I do not change.

Who am I?

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

Nodes are shown below and you need to connect them based on the following rule: Every node can be connected to the number of nodes inside them, i.e. the first node there is a value of 1 which indicates that the first node can connect to exactly one node only.Can you do it?

How much will a 38° angle measure when looked at under a microscope that magnifies ten times?

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?

A mile-long train is moving at sixty miles an hour when it reaches a mile-long tunnel. How long does it take the entire train to pass through the tunnel?

What are the 50th, 63rd and 100th numbers in the sequence below?
4, 5, 8, 8, 9, 9, 12, 13, 13, 13, 17, 18, ...

There was a strange boy who was born before his father. How can this be possible?