If I remove one from eleven it becomes Ten and if I remove one from nine also becomes Ten. How?

Can you solve this amazing hard number series problem?
7, 8, 10, 12, 16, 18 ?

There is a circular car race track of 10km. There are two cars, Car A and Car B. And they are at the exact opposite end to each other. At Time T(0), Both cars move toward each other at a constant speed of 100 m/seconds. As we know both cars are at the same speed they will always be the exact opposite to each other.
Note, at the center, there is a bug which starts flying towards Car A at time T(0). When the bug reaches car B, it turns back and starts moving towards the car A. The speed of bug is 1m/second. After 5 hours all three stop moving.
What is the total distance covered by the bug?

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 ?

What begins with T, ends with T, and has T in it?

A thief is convicted in Mexico. He gets the death penalty. The judge allows him to say the last sentence to determine how the penalty will be carried out. If the thief lies, he will be hanged, if he speaks the truth he will be beheaded. The thief tells the last sentence and to everybody's surprise some minutes later he is set free because the judge cannot determine his penalty. What did the thief say?

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _

John is asked to stand behind Jacob and Jacob is asked to stand behind John. Both of them feel confused about it and don't know what to do?

But it is quite possible, do you know how?

What can run but never walk, have a mouth that never speaks, have a head that never weeps, and have a bed but never sleeps?

How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?