Which number should replace the question mark?

A Shopkeeper collects 71 rupees in the form of 20 paisa and 25 paisa.
He collects a total of 324 coins.

Can you tell me how many number of 20-paisa and 25-paisa he got?

Luis Garavito killed Density x Volume.

Who is Luis Garavito ?

The following alphametic has only one solution. Can you find it?
ENLIST + SILENT + LISTEN = ANAGRAM

PS: You may start the number from 0.

A man hijacks an aeroplane transporting both passengers(8 of them) and valuable cargo. After taking the cargo, the man demands nine parachutes, puts one of them on, and jumps, leaving the other eight behind. Why did he want eight?

Bea Smith, Vera Bennett, Franky Doyle and Doreen Anderson were in Wentworth Prison for murder. But their behaviour in the jails is appreciated by the warden and the warden decided to give all these 4 prisoners 11 cupcakes. They all like cupcakes and they had all cupcakes in no matter of time but they do not know how many cupcakes each individual had. Therefore Bea started the conversation Bea: "Hey T-Vera, did you have more cupcakes than I had ?"Vera: "I do not know girl, Hey Franky, did you have more cupcakes than I had ?".Franky: "I do not know"Doreen replied instantly: "I know how exactly how many cupcakes each of you had?" So can you tell how many cupcakes each of them had?

What's the next in the series?

H, Be, F, S, Mn, Kr, In, Gd, Tl, ?

Find the next number in the series.
1 10 24 43 67 ?

I have Rs.50 and I spend it in the way as below.

How many sides does a circle have?