What has no start, end, or centre?

If eleven plus two equals one, what does nine plus five equal?

Two fathers and two sons decided to go to a shop and buy some sweets upon reaching. Each of them bought 1 kg of sweet. All of them returned home after some time and found out that they had 3kg of sweets with them.

They did not eat the sweets in the way, nor threw or lose anything. Then, how can this be possible?

What word is pronounced the same if you take away four of its five letters?

I am a type of vehicle that has two wheels and is powered by humans. What am I?
Hint 1: You can ride me for exercise.
Hint 2: I am environment-friendly.

There is a hypothetical state between the USA and Mexico border 'Tango'.
Here 70 percent of the population have defective eyesight, 75 percent are hard of hearing, 80 percent have Nose trouble and 85 percent suffer from allergies, what percentage (at a minimum) suffer from all four ailments?

Solve The below Equation:

ALFA + BETA + GAMA = DELTA

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

I’m light as a feather, yet the strongest person can’t hold me for five minutes. What am I?

People put me on the table and cut me but do not eat me. What am I?