In a school, there are four subjects. Seventy percent of students study English, seventy five percent of students study Science, eighty five percent of students study Mathematics and eighty percent of students study Spanish.

Can you calculate the percentage of students that study all four subjects?

You are given 16 witch hats. The hats are divided in four different colours – red, blue, green and yellow. Every colour has been assigned to four hats. Now each of the hat will be glued with a label of an arithmetic sign – ‘+’, ‘-‘, ‘x’ or ‘/’. But you can label one sign only once on one colour. In such an arrangement, the hats can be uniquely defined by its colour and symbol.

Can you arrange all the 16 hats in a 4x4 grid in a fashion that no two rows and columns have a repetition of colour or sign?
We have arranged four hats in the below picture to assist you.

A wife and her husband were driving in their car on the highway. All of a sudden, they ran out of gas. So the husband said to the wife, 'Now, you stay here. I will go down the highway to the nearest gas station, and it will be about 1 hour. Just listen to the radio and read some books, and remember to lock all the windows and doors. I will leave the keys with you.' So, off the husband went, and the wife first locked ALL the windows and doors. Next, she turned on the radio, and this is what she heard on the news report:
'THERE IS A MURDERER ON THE LOOSE. HE WAS LAST SEEN ON THE HIGHWAY, WEARING ALL BLACK, ABOUT 5 FOOT 11 INCHES. PLEASE, BE AWARE AND CONTACT THE POLICE IMMEDIATELY.' The wife got very scared. She turned off the radio and double-checked the locked doors. Then she saw the murderer, only a couple of feet away from the car. An hour later, the husband returned to his car. Inside the car, his wife was DEAD, she had been murdered. All the windows were still locked, and the doors. No windows were broken, and the car was in PERFECT condition. No scratches or anything, it was the same way as when he left it. How did the murderer kill the wife?

What makes this number unique: 8,549,176,320?

After teaching his class all about Roman numerals (X = 10, IX=9 and so on) the teacher asked his class to draw a single continuous line and turn IX into 6. The teacher's only stipulation was that the pen could not be lifted from the paper until the line was complete.

Which digit occurred maximum times between the number 1 and 1000?

I have 50 feet long of cloth, I need to create 50 handkerchiefs each size of 1 foot. I take one minute to cut a 1-foot handkerchief. So how long will it take to cut 50 handkerchiefs?

Two natural numbers have a sum of less than 100 and are greater than one.

John knows the product of the numbers and Jacob knows the sum of numbers.

The following conversation takes place between them:
John: 'I am not aware of those numbers.'
Jacob: 'I knew you wouldn't be. I am not aware myself.'
John: 'Now I know them!'
Jacob: 'Now I know them, too!'

What are the two numbers?

A man died and leaves Rs.10,000 in his will. There are 6 beneficiaries- his 3 sons and their wives. The 3 wives receive Rs.3960 of which Priyanka gets Rs.100 more than Tanu and Neha gets Rs.100 more than Priyanka.
Pramod gets twice as much as his wife, Tushar gets the same as his wife, and Prashant gets 50% more than his wife.

Who is married to whom?

As a whole I am both
safe and secure.

Behead me and I become
a place of meeting.

Behead me again and I am
the partner of ready.

Restore me, and I become
the domain of beasts.

What am I?