What does this rebus mean?

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John was running from 40 thieves. John has got 3 gold boxes which weigh as 4kg, 2kg, and 1kg respectively. A witty man asked John to stay with him for seven days in exchange for 1kg gold per day. John needs to stay there for seven days and also do not want to give the witty man any advance. How can John pay for his seven days stay?

Can you find out the next digit in the following series ?

0, 0, 1, 3, 2, 6, 3, 9, 4, 12, 5, ?

What does a man do only once in his lifetime, but women do once a year after they are 29?

Which tank will fill first?

What is the next number in this series?

4,12,84,3612....

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?

I am the beginning of everything, the end of everywhere. I'm the beginning of eternity, the end of time and space. What am I?

If you drop a 15 kg iron bar and a 5 kg bag of cotton from a height of 50 meters which will reach the ground first?

This puzzle is for Harry Potter fans. Do you know why Tom Riddle is called Lord Voldemort?