How do you go from 98 to 720 using just one letter?

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?

For an extra income, John decided to work at a Hotel for one hour daily. The manager offers him that they will pay him $11 after every 11 days.
However, John offered a different proposition to the manager. The offers stand as:
He will be paid just a penny on his first day.
Two pence will be paid on the second day,
Four pence will be paid on the third day.
And so on till the 11th day.

Should the Hotel manager accept his offer?

Andrew’s doctor gives him three pills and tells him to take one every half hour. How much time will have passed by the time Andrew’s taken all three pills?

why number 8549176320 is one of a kind?

In a boat, the father of a sailor's son is sitting with the son of the sailor. However, the sailor is not present on the boat.

Can this even be possible?

A man wants to cross the pit of fire which is 25 feet in length and he has 2 planks(fire resistant) 19 feet in length. How can he cross the pit of fire alive?

You can see it everyday, But cannot touch it at will. What is it?

If you drop me I’m sure to crack, but give me a smile and I’ll always smile back. What am I?

Place the numbers from 1 to 9 in the circles in a manner that each side of the triangle sums up to 17.