I need to know how to make powers in Scratch! The reason is… my oldest brother (who's a computer science major) has just given me a challenge to create a program that calculates Fibonacci numbers. So I looked up the formula, and it says this: (1.168)n÷√5 (the ‘n’ is supposed to be a power), and then you round it to the nearest whole number. I can do most of the formula in Scratch, but I can't figure out how to do the power! I've tried and tried, and I can't do it!! I need help!







l0ve1y

You don't neccessarily need that formula.
You could just use the recursive formula: n(a) = n(a-1) + n(a-2)

Well, powers are multiplied multiples. So as you may know, 3^2 is 3*3. You could use this method, or there is an operator that MAY work. At the very bottom of the operator page is a green block. This appears to have square roots in it and similar functions. That might work. (Maybe .3.)

dracae wrote:

You don't neccessarily need that formula.
You could just use the recursive formula: n(a) = n(a-1) + n(a-2)

And what does ‘a’ stand for?

l0ve1y wrote:

I need to know how to make powers in Scratch! The reason is… my oldest brother (who's a computer science major) has just given me a challenge to create a program that calculates Fibonacci numbers. So I looked up the formula, and it says this: (1.168)n÷√5 (the ‘n’ is supposed to be a power), and then you round it to the nearest whole number. I can do most of the formula in Scratch, but I can't figure out how to do the power! I've tried and tried, and I can't do it!! I need help!
l0ve1y

Well, I had a project on this, but apparently my test account didn't get transferred or something.

Anyway, here's how I did it:
when green flag clicked
set (number) to (1)
set (prev. number) to (0)
add (prev. number) to (Fibonacci numbers)
add (number) to (Fibonacci numbers)
repeat (however many you want) times
set (number) to ((number)+(prev. number))
set (prev. number) to (item [last v] of (Fibonacci numbers)
add (number) to (Fibonacci numbers)

This should work. If it doesn't tell me. I hope this is what you meant.

x ^ y = e ^ ( y * ln(x) )

Look amongst the green operators (in the drop-down that shows “sqrt”), and you'll find both e^ and ln (that's known as “natural logarithm”) - so you can do it via those.

Try it with, for example, e^(5*ln(10)), and you'll get the answer 100000, which is 10^5.

Here's the easy way to do it: http://scratch.mit.edu/projects/10330799/
See inside to see how I did it!
Hope I helped!

Yeah, I think you should do the original way of Fibonacci, the formula isn't exact as the phi is an estimate.

kayybee wrote:

Yeah, I think you should do the original way of Fibonacci, the formula isn't exact as the phi is an estimate.

Of course, you could just use the rounding block to make it.
Though other ways are more convenient. : |

Here. This project has square numbers, triangular numbers, and Fibonacci numbers.

Using “round( 1.618034^n / sqrt(5) )” should be fine to find the nth value (assuming you don't want to find all the digits, accurately, as n gets into the hundreds).

i.e. with the e^ and ln: round( e^(n*ln(1.618034)) / sqrt(5) )

I still think you should do it the original method by calculating numbers by adding the previous two.

kayybee wrote:

I still think you should do it the original method by calculating numbers by adding the previous two.

I agree with kaybee. This method is easier, and makes more sense.

Well, it'll certainly be more accurate to use the addition formula - that should be a more accurate computation over more digits than using the e^ and ln.

Does quick check…

Yes, using e^ and ln it breaks down when n=43 (that's even with a more accurate value of 1.6180339887), which means those operators must be pretty low accuracy. Using addition it breaks down by n=79.

OK, here's something that's a bit more of challenge then…

Write a script in Scratch that uses the addition method to calculate Fibonacci numbers, but which *doesn't* break down.
In fact, make it work to at least n=5000, if not theoretically infinite - assuming you have that much memory and time
(Hint: use the numbers as strings and work in chunks that it can deal with…)

Once you've done that you should be well on your way to figuring out how you could do things like calculate pi to many thousands of places…
(Has anyone done that yet with Scratch…?)
Hmmm, should we rename this topic “Fun with maths”…?

I have made a really simple engine that doesnt involve triangle or Fibonacci or decimal numbers.

All you have to do is make costumes one to superpowers costume and one do normal costume. Then

Please don't necropost.