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

There once were seven dwarfs who were all brothers. They were all born two years apart. The youngest dwarf is seven years old. How old is his oldest brother?

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?

Using mathematical symbols like +, -, and x in order to make the equations correct. Replace # with the above-given symbols.

9 # 8 # 7 # 6 # 5 # 4 = 91

Can you find out which number multiplied by itself will give the output as 12345678987654321?

A network of 20 x 10 squares is given to you.

Can you calculate how many unique squares and rectangles can be formed combining two or more individual squares ?

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

John replied, when asked how old he was. In 2 years he will be twice as old as he was five years ago.' How old is he ?

There are two candles. Both will only burn exactly for an hour. How will you use these two candles to measure forty-five minutes?

A Shopkeeper collects 71 rupees in the form of 20 paisa and 25 paisa.
He collects a total of 324 coins.

Can you tell me how many number of 20-paisa and 25-paisa he got?