A Doctor always sneezes before the rain. Doctor sneezes, Will it rain?

Analyze and find the missing item in the sequence:
16, 06, 68, 88, __, 98

Can you find out what is missing?

1 3 5
2 4 ?

Hint: It's not six. Think out of the box.

Today, I celebrated my 32nd birthday but I was born in 1972.
How is this possible?

There are six people in a family namely M, N, O, P, Q and R.

R and O are brother and sister.

N is the brother of Q's husband.
P is the father of M and grandfather of R.

How many male members are in the family?

Below, you will find the mathematical proof that 10 equals 9.99999?. But is that possible or there is something wrong about it? Can you find the error?

x = 9.999999...
10x = 99.999999...
10x - x = 90
9x = 90
x = 10

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

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

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?