What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

Decode below rebus
D
N
A
T
S , D

Can you count the number of lines in the below picture?

A time long back, there lived a king who ruled the great kingdom of Trojan House. As a part of the renovation of the kingdom to meet future security needs, he asked his chief architect to lay down a new play in a manner that all of his 10 castles are connected through five straight walls and each wall must connect four castles together. He also asked the architect that at least one of his castles should be protected with walls. The architect could not come up with any solution that served all of King's choices, but he suggested the best plan that you can see in the picture below. Can you find a better solution to serve the king's demand?

Can you place six X (crosses) in below board without making three in a row in any way ?

12345 a famous South Indian actor
567 is a path in jumbled form
8 & 10 are same letters
9 is one among the first six alphabets.
WHO AM I?

A man dies of old age on his 25 birthday. How is this possible?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Look at this sequence from top to bottom. What is the next number in the sequence?
1
11
21
1211
111221
312211

Why is a river so rich ?