I’m tall when I’m young, and I’m short when I’m old. What am I?

What does this mathematical rebus means ?

There are three identical triplets sisters. Demi is the oldest of them all and she always speaks the truth. Diana is the next one who is a liar always. Drew, the youngest of them all speaks both truth and lies randomly.

On a rainy day, a family friend Victor visited them. Since there were starkly identical, he was not able to recognize them. Thus to clarify, he asked one question to each one of them.

He started with the one standing on the left and asked, 'Which sister is in the middle of you three?' She answered, 'That's Demi.'

Then, he asked the one standing in the middle, 'What is your name?' She answered, 'I am Drew.'

Finally, he asked the one standing on the right, 'Who is standing in the middle?' She answered, 'She is Diana.'

Victor was left baffled. He asked the questions three times and received different answers every time.

Can you tell who was who?

Our product and our sum always give the same answer. Who are we?

The product of three consecutive numbers is 7980.
Then the sum of these consecutive numbers would be?

How can you make the following equation true by drawing only one straight line: 5+5+5=550 ?

In 1990, a person is 15 years old. In 1995, that same person is 10 years old. How can this be?

I make a loud sound when I’m changing. When I do change, I get bigger but weigh less. What am I?

I am an eight letter word and I am a computer terminology.
The second, third and fourth letters make an animal.
The fourth, fifth, sixth, seventh and eighth letters make a weapon.
The first, second, third and fourth letters can be taken as an outcome of any exam.
The fifth, sixth, seventh and eighth letter combine to form a high end typing software.

Can you tell who am I ?

What is the largest number you can write with just 3 digits?