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Paul Jennings

HIS LIFE BOOKS LETTERS ACTIVITIES

 Here are some letters children have written to him

Bridget has picked up on a mathematical problem in one of my stories, one that I didn't even know the answer to!

Dear Puffin Books, I was reading 'Next Time Around' in Unbearable by Paul Jennings and on page 43 it says something about a sum where you have to figure out how long it will take to fill the bath if it fills with 2 litres a minute and empties half a litre a minute.  This sum is impossible to do because it doesn't say how much the bath can hold. The answer (3 minutes) is on page 48.  If this answer is true then it makes the bath extremely small. I would like to know if this answer is true and if it isn't what the real answer is. Yours Sincerely Bridget

Dear Bridget

Well done! You are the first person to have queried the answer to the bath problem in my story 'Next Time Around'. I may be able to write pretty good stories, but as you can tell, my mathematical skills leave a little bit to be desired!

I have passed your letter on to an Engineering Consultant, John Ulph, and he has replied with the answer. I will attach a copy of the letter below for you. (It is the one in red). I would also like to post your letter on my Web Page (without your address), for others to see - I think this will be of great interest to many other readers.

Again, Congratulations on being such an attentive reader Bridget, and thanks again for bringing this discrepancy to my attention.

Yours truly,

Paul Jennings

Paul,

Your reader Bridget, has raised an intriguing question. (I think we may have an engineer in the making).

At first view, if 2 litres per minute is running into a container and 1/2 a litre is running out, the sum effect would appear to be the same as 1 1/2 litres per minute running into a container without a plughole.

So 3 x 1 1/2 equals 4 1/2 litres in the 3 minutes mentioned in the story.

But life wasn't meant to be easy (who said that?).

The real world can be somewhat different.

Firstly, it initially depends on where the plughole is in relation to the water entry. If they are at either end of the bath, then it will take some time for the water to reach the plughole and then it will have to fully cover it before 'full' flow out can start. Of course, also the bottom of the bath may not be flat.

Secondly, the rate of outflow will change as the level of the water increases. This is due to the increasing weight of the water above the plughole. Bridget might like to try a little experiment…..

Take an old plastic drink bottle and fill it with water. Then punch a small hole (say with a skewer) in the side near the bottom and another, on the other side, halfway us. (To stop most of the water leaking while you do this, tightly seal the top of the bottle with its cap).

Now remove the cap.

You will notice that the water flowing from the bottom hole spurts out further than that from the hole higher up. This is because the weight of the water above the bottom hole is more than that above the higher hole.

Now take 2 glasses of the same size and let each fill from a different hole at the same time. The glass catching water from the bottom hole fills quicker.

So, conceivably, since the inlet rate of water is constant, with enough time and if your bath was deep enough, and the height of the water could rise to a point where its weight would force the water out of the plughole at the same rate as it was flowing in…… the bath would then never fill.

Anyway, getting back to your story…… You were of course describing a deluxe (because it has a plughole) birdbath.

As for why only a little, if any, water leaks from the capped bottle with the holes in the side, I leave that for Bridget to discover and tell you.

Kind Regards

John Ulph

Marion has made some great observations during her reading.  See if you know the answers.

Dear Paul,

Hi! I have a few questions and observations about your books and I hope that you can answer them for me.

First I would like to say how I have noticed quite a few jokes that were entwined into your amazing twisted tales.  I noticed that in the story 'pubic hair' that Riah Devahs was actually shaved hair spelled backwards.  I was also wondering how did Riah die?  In the story 'Too many rabbits' in the second page of the story on the 13th line, you wrote you have to strike while the lion is hot, and I was wondering was this because the boy in the story was looking for an animal for a pet?

In the story 'Seeshell' I was wondering is that meant to be like sees hell?

In the story 'Nails' what was Leham's father looking for every day that he went to the beach?  I was also wondering are you writing any new books?  Because I have read all your books so far and I want to read another one.  Recently I crossed the Simpson Desert with my family and all I did was read your books again and again.

Thankyou

Marion...................................