h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Not 5, sorry

I've spent a little more time thinking about it (2 mins rather than 30 secs) and have come up with 10 now.

Any advance on 10?

I have just found the eleventh, but cannot see any more.

¦ xxxxx

¦ xxxx
¦ x

¦ xxxx
¦ _x

¦ xxx
¦ xx

¦ xxx
¦ x_x

¦ x
¦ xxx
¦ __x

¦ _x
¦ xxx
¦ _x

¦ xxx
¦ __xx

¦ _x
¦ xxx
¦ x

¦ x
¦ xxx
¦ x

¦ xx
¦ _xx
¦ __x

I hate to say this, but...

11 isn't the answer

I've just seen another one:

¦ xxx
¦ x
¦ x

Is it 12?

It certainly is!

They're called 'pentominoes'. The full set (including reflected ones) can be seen here: http://en.wikipedia.org/wiki/Pentomino

Over to you...

Well, I'd say 12.

We had a puzzle than involves these shapes (which I've seen referred to as Pentonimoes). The aim of the puzzle was to fit the shapes into the box that they came in. Dad might still have it somewhere. It looked something like this when completed:

http://puzzler.sourceforge.net/docs/images/pentominoes6x10.png

We had another puzzle that was similar too. The difference was that the component blocks were hexagons, rather than squares.

Geggs

An 18-wheeler is crossing a 4 kilometer bridge that can only support 10,000 kilograms and that's exactly how much the rig weighs. Halfway across the bridge a 30 gram sparrow lands on the cab, but the bridge doesn't collapse. Why not?
P.S. for fellow engineers, ignore safety factors and yield strength vs ultimate strength.

It will have used up some of it's fuel by the time it got halfway across that 4 kilometer bridge. So it would not weigh as much by then.

Correct; your go.

For what is this a mnemonic?

" Bless My Dear Aunt Sally! "

I think that's the pecking order of mathematical operations - we used to call it BODMAS at school.

Brackets, Multiplication, Division, Addition, Subtraction

Some say BIDMAS, with I for Indices, I think.

Q. Which two-digit number becomes its hexadecimal equivalent when reversed?

53 in decimal is 35 in hex

Well done Mikey - you score A/A for that.

Over to you...

A man goes running through a wood. Afterwards, he works out how long it takes him to get half way through and he tells a friend. His friend says that he could run two thirds of the way into the wood in the same time. The runner says that that isn't possible. How does he know?