How can you make number one disappear by adding something to it?

What will be the best approach to finding all the prime numbers less than 75 that leave an odd reminder when we divide them with 5?

We have four gears with below features=> Both Gear A and D has 60 teeth=> Gear B has 40 teeth=> Gear C has 20 teeth=> Every two minutes, Gear B makes 25 full turns.What is the relative speed of Gear A and Gear B?

Here is a conversation between a couple who both are software professionals.

Husband: Hey! What is your date of birth?
Wife Replied Angrily: It is 591062400
Husband after doing some calculations replied, "Got It".

What is the DOB of the wife?

Can you identify the hidden rebus in the image below?

What is the Surname of Barbie Doll?

Two prisoners Jack and Jill are locked in a cell.
There is open window approx 40 feet above the ground of the cell.
They are never able to reach there.

Then they plan to escape by a tunnel and they start digging out.
After digging for more than 20 days, Jill comes with the different plan and they escaped.

what was the plan ?

Decode below three cipher riddles:

26 L of the A
7 D of the W
1000 Y in a M

A Child was born in Lahore, Pakistan.

Still child is not a Pakistani citizen.why ?

You Throw The Outside, Cook The Inside
Eat The Outside, Throw The Inside.

What Is It?