The centre of the third figure is empty. What digit should fit inside?

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

Who am I?

No matter how little or how much you use me, you change me every month. What am I?

Can you solve the photo plexer logic ?

I have a clock(12-hour format) and both the needles of the clock overlap at 12:00.
After how much time, they will overlap again?

Three men in a cafe order a meal the total cost of which is $15. They each contribute $5. The waiter takes the money to the chef who recognises the three as friends and asks the waiter to return $5 to the men.

The waiter is not only poor at mathematics but dishonest and instead of going to the trouble of splitting the $5 between the three he simply gives them $1 each and pockets the remaining $2 for himself.

Now, each of the men effectively paid $4, the total paid is therefore $12. Add the $2 in the waiters pocket and this comes to $14. Where has the other $1 gone from the original $15?

What has many keys but can’t open a single lock?

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

Find The Next Number In The Sequence

30 10 15 13 0 16 -15 ?

Find three numbers such that

* When we multiply three numbers, we will get the prime numbers.
* The difference between the second and the first number is equal to the third and second.