How many words can a pen with half refill write?

Until it is measured, not known. Yet how you miss it when it has gone. What is it?

John is looking at Jenifer, but Jenifer is looking at Jacob. John is married, but Jacob is not.

Is a married person looking at an unmarried person ?

By moving exactly three matchsticks can you make the below equation true.It can be solved by 3 ways.

The more you take me, the more you leave me behind.
Who Am I?

Can you make four (4) nines (9) equal 100?

Can you find the missing letter in the sequence?
S - T - I - L - ? - T - F - Y - C

Which three-digit number, made of consecutive digits, like 567, is 2 less than a cube and 2 more than a square?

How much will a 38° angle measure when looked at under a microscope that magnifies ten times?

If two's company, and three's a crowd, then whats four and five ?