What number when divided in half becomes zero?

There are 2 sand hourglasses.

The small one can measure 5 hours and the large one can measure 7 hours.

How can we measure 16 hours with 2 sand hourglasses running together ?

I am a white box having no key or lid.
Yet there is a golden treasure inside it.

What Am I?

I welcome the day with a show of light, I stealthily came here in the night. I bathe the earthy stuff at dawn, But by noon, alas! I'm gone.

1 + 9 + 8 = ?
considering, 28 + 8 + 92 = 10

What is more useful when it is broken?

1 rabbit saw 9 elephants while going to the river. Every elephant saw 3 monkeys going toward the river. Each monkey had 1 parrot in each hand. How many animals are going towards the river?

John was born on March 5, 1970, in Delhi, India. Jacob was born 25 days before John. The year when they took birth, Republic Day fell on Monday.

Can you find out on what day was Jacob born?

The day before yesterday I was 25 and the next year I will be 28. This is true only one day in a year. What day is my birthday?

Can you find out what is missing?

1 3 5
2 4 ?

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