What is always in front of you but can’t be seen?

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.

I had an infinite supply of water and 5 litres and 3 litres jars.

How would you measure exactly 4 litres in the least number of steps?

Can you find a pattern and the missing number in the series given below?

100, 155, 258,? , 584, 819.

Count the Triangle in the figure given below:

Tell me the Hindi name of a Vegetable which if we remove 1st word will become a precious Stone and by removing the last word it will become a sweet eatable.

Find the missing number in the series below

13 -21 34 -55 ? -144

What comes
Once in a Year
Twice in a Month
4 times in a Week
6 times in a Day

Kareena is older than Katrina and younger than Karishma. Isabelle is younger than Bipasha and Karishma. Bipasha is older than Karishma. If Kareena and Isabelle are the same age, who's the youngest?

What goes through cities and fields, but never moves?