How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

In a school, 280 students studied chemistry, 254 students studied physics and 280 students studied biology.

97 students studied chemistry as well as physics, 138 students studied physics as well as biology and 152 students studied chemistry as well as biology.

73 students studied all the three branches.

Can you find out the total number of students?

If we add four times the age of John four years from now to five times his age five years from now we get ten times his current age.

How old will John be two years from now?

How many triangles are there on the puzzle below?

I guess 76.8% of readers will like this riddle.

What's the least number of people should read this post?

A 3 digit number is such that it's unit digit is equal to the product of the other two digits which are prime. Also, the difference between it's reverse and itself is 396.

What is the sum of the three digits?

If 5 cats catch 5 mice in 5 minutes, how long will it take one cat to catch a mouse?

Can you solve below mathematical equation?

2^1234 - 2^1233

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

An octopus has 8 legs. A hippogriff has 6 legs and 2 pairs of wings. A sphinx has 6 legs and one pair of wings. Now we have all 3 kinds and a total of 18 insects in a cage. We have a total of 118 legs and 20 pairs of wings. How many insects do we have of each kind?