Which Number is the odd one out?

A) 7145
B) 2716
C) 5321
D) 4135

What's the only room from which no one can enter or leave

Can you write down eight eights so that they add up to one thousand?

What does this rebus riddle means ?

Can you count the number of matches in the picture below ?

All Marigolds are flowers.
Few Flowers are used to make colors.
Therefore, some Marigold are used to make colors.

True Or False?

I am a prime number.
The double of myself is equal to the square of me.

which number am I?

Find a 9-digit number, which you will gradually round off starting with units, then tenth, hundred etc., until you get to the last numeral, which you do not round off. The rounding alternates (up, down, up ...). After rounding off 8 times, the final number is 500000000. The original number is commensurable by 6 and 7, all the numbers from 1 to 9 are used, and after rounding four times the sum of the not rounded numerals equals 24.

When a clock is observed, the hour hand is at a minute mark and the minutes hand is six minutes ahead of it.

When the clock is observed again after some time, the hour hand is precisely on a different minute mark and the minute hand is seven minutes ahead of it.

Can you calculate how much time has elapsed between the two observations?

Below the four parts have been reorganised. The four partitions are exactly the same in both arrangements. Why is there a hole?