Cleave Books Puzzle Trio 7
19. 
I recently found just the things I wanted at a carboot sale. The way they were priced was interesting. 

 5  for  10p 

12  for  18p 

14  for  20p 

19  for  24p 


I eventually worked out the 'logic' of the prices.
What did 11 cost me?

20. 
Kim wishes to measure out 4 litres of water, but has only two jugs which, when full, hold 3 litres and 5 litres respectively and have no other markings on them.
Plenty of water is available from a tap.
How can Kim measure out exactly 4 litres?

21. 
A deltahedron is a 3dimensional shape all of whose faces are equilateral triangles.
The simplest of these is a regular tetrahedron, which is made of 4 equilateral triangles.
So it has 4 faces, 4 vertices, and 6 edges.
The deltahedron I have has 9 vertices.
How many faces does my deltahedron have?

