What is black when you buy it, red when you use it, and gray when you throw it away?

Can you complete the sequence puzzle?

AR TA GE CA LE VI LI _

How many words can a pen with half refill write?

There was once a college that offered a class on probability applied to the real world. The class was relatively easy, but there was a catch. There were no homework assignments or tests, but there was a final exam that would have only one question on it. When everyone received the test paper it was a blank sheet of paper with a solitary question on it: 'What is the risk?'.Most students were able to pass, but only one student received 100% for the class! Even stranger was that he only wrote down one word!
What did he write?

My friends called me Iron59 because my parents are a chemist and a mathematician. What is my real name?

I cannot talk, but I always reply when spoken to. What am I?

How many cubic feet of dirt are in a hole of one foot deep, three feet long, and two feet wide?

John was writing his first book. After saving the document, he locked his laptop with a password and mentioned some phrases for the hint box.

A friend of his tried opening his laptop but found out that it was password protected. Following is the hint that appeared.
1 mobile 3 books 2 roars 1 night 4 balls 2 lighters 1 ghost 1 hat 3 watches.

Can you help him in cracking the password?

There is a five-letter word which has 3 consonants(all are same) and 2 different vowels.
Also, something wrong is associated with the word.

Can you name it?

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