Discussion about math, puzzles, games and fun.   Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ • π ƒ -¹ ² ³ °

You are not logged in.

## Post a reply

Write your message and submit
|
Options

## Topic review (newest first)

MathsIsFun
2005-12-14 17:25:54

That is a great website ... what a collection.

I had to say to myself "later!" or I would get nothing done today.

justlookingforthemoment
2005-12-14 09:18:27

These optical illusions are great!

I see what you mean about temperature. It's kind of like saying 'I'm three times as short as you'. How can you be twice as short? It makes more sense when you say 'I'm a third as tall'.

I spent a long time playing with many more puzzling ones here:

http://www.michaelbach.de/ot/

MathsIsFun
2005-12-14 07:29:47

That is one of the best optical illusions ever!

Quite right about "twice as cold", it really makes no sense for two reasons:

1. Temperature is just an arbitrary scale. To have it make sense, you would need to measure the amount of heat energy. Then you could say "this has twice as much heat".

2. Cold is just the absence of heat, so saying "twice as cold" is like saying "twice as poor".

Having said that, -20°C would still be the "commonly accepted" answer

mathsyperson
2005-12-13 23:13:07

I get what MathsIsFun gets. Nothing at first, then a bright white dot where there should be nothing. It also has a hint of green for no apparent reason. Did anyone else get that or are my eyes weird?

The question raises an interesting point. How can you calculate how much is twice as cold?

Doing the same thing with °C, °F and K would return different answers. Also, what is twice as cold as 0°? What's the difference between twice as cold and twice as hot?

MathsIsFun
2005-12-13 17:09:14

I get a phantom bright dot ... the eye over-compensates for the missing dot I think.

justlookingforthemoment
2005-12-13 17:05:45

What are you meant to do?

I've been staring at the middle and the flashing appears to be changing speeds, so I presume that's what's meant to happen.

MathsIsFun
2005-12-13 17:04:00

Cool optical illusion !

(The website has more, but also LOTS OF ADS)

noorey711
2005-12-13 17:02:39

oh..
Thank you!!!

justlookingforthemoment
2005-12-13 16:57:42

You were on the right track, but instead of dividing, you should multiply.

-4 x 5 = -20°C

So, the coldest day was -20°C. Brr!

noorey711
2005-12-13 16:02:58

Robin Reed reported that the coldest day on record for his town was five times colder than

yesterday's temprature, -4°C. What was the temprature of the coldest day in record in

Robin Reed's town?

do I have to divid -4÷5= [-4]÷[5]= 4÷5= -0.8

is this right?

## Board footer

Powered by FluxBB