I think he meant

http://www.mathsisfun.com/puzzles/band- … earth.html

and I think this was answered at the time.

Have a look and decide for yourself.

Bob

]]>welcome to the forum. We need the question at least so that we can give answer.]]>

Thanks for your reply. All clear now!

John

]]>The earlier answers are just algebraic versions of your (partially) number solution.

Put C = 40 000 000 and the two come to the same thing.

Bob

]]>Just had a crack at the Band Around the Earth problem. I get the right answer, but using a different method. I don't understand how the following subtraction occurs in the example given:

Before: Original Circumference = 2 × pi × R

After: Original Circumference + 10 = 2 × pi × (R + Gap)

to give: 10 = 2 × pi × Gap

The main problem that I have is that one cannot divide R out of the equation as it is added to Gap, nor can it be subtracted as it is multiplied by 2 pi.

If someone could explain this to me I'd be very grateful! Just to give some more info, my solution works by substituting the following two equations together:

R + Gap = 40,000,010 / 2 x pi

R = 40,000,000 / 2 x pi

to give:

(40,000,000 / 2 x pi) + Gap = 40,000,010 / 2 x pi

and thus:

Gap = (40,000,010 / 2 x pi) - (40,000,000 / 2 x pi)

The answer comes out in metres.

Many thanks in advance to anyone who can help!

John

Did you read my earlier post?

10 = 2 × pi × Gap

So, the Gap = 10 / (2 × pi) = 1.6m

That looks like 10 meters to me.

If you're still not convinced try converting all measurements into Km.

You'll get an answer of 0.0016 Km

Bob

]]>yes you are right.you could express it in km but it wouldn't change anything cuz the stuf in kilometres cancels out.

]]>I think it's this one

http://www.mathsisfun.com/puzzles/band-around-the-earth.html

to djohnstone3

The solution uses R without specifying units, so they could be meters.

When you subtract those units (whatever they are) all disappear leaving a formula for the gap, again no units specified.

So if you substitute a value of 10 meters the answer will be in meters.

Confused?

How about this?

My friend is 5 feet 8 inches tall.

I am 5 feet 6 inches tall.

How much taller is my friend?

5 feet 8 inches - 5 feet 6 inches = 2 inches. I don't have to change the feet to inches to do this.

Bob

]]>Welcome to the forum!

Where is the problem?

]]>welcome to the forum.

you are probably right but it would be nice if you could post the problem here.

]]>