How many times in a given day, minutes and hour clock comes in a straight line ?

Christina has four daughters, and each of her daughters has a brother. How many children does Christina have?

I am taken from a mine and shut up in a wooden case, from which I am never released, and yet I am used by almost every person. What am I?

Which English verb becomes past tense just by rearranging the letters?

In a competitive exam, each correct answer could win you 10 points and each wrong answer could lose you 5 points. You sat in the exam and answered all the 20 questions, which were given in the exam.
When you checked the result, you scored 125 marks on the test.

Can you calculate how many answers given by you were wrong?

Samuel was out for a walk when it started to rain. He did not have an umbrella and he wasn't wearing a hat. His clothes were soaked, yet not a single hair on his head got wet. How could this happen?

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?

What number comes next in the series?

5 15 5 18 5 24 14 20 _

Can you make numbers like 24, using numbers 3,3,7 & 7 with any arithmetic operator?

what does this picture(rebus) riddle means ?