# Fractions in fibonacci series

• 01-08-2008
Jamkirk
Fractions in fibonacci series
i've been sitting here for 2 hours searching through info sites
and forums getting absolutely nothing out of it. its a simple
problem i have. how to add fractions in c:

where a/b + c/d == x/y

can someone point me in the right direction? :)
• 01-08-2008
robatino
You treat fractions as ordered pairs of integers, and reduce them to lowest terms if they aren't already, using the Euclidean algorithm

http://en.wikipedia.org/wiki/Euclidean_algorithm

to compute the GCD of the numerator and denominator and then divide both by it. In the case of adding fractions, use the formula

a/b + c/d == (ad + bc)/bd

followed by reduction to lowest terms as described above.
• 01-10-2008
kcpilot
You better try again: That formula does not work for the following two fractions of adding 1/3 and 1/5. According to the formula above, this would be equivalent to 3/5, whereas the real answer is 8/15. Or is my arithmetic that bad??
• 01-10-2008
anon
Yes, your arithmetic is bad :) (1 * 5 + 1 * 3)/(3 * 5) == 8 / 15

If you tried it programmatically then a / b * c != a / (b * c) although the parenthesis should not be required by human conventions (multiplication has higher precedence in algebraic notation?)
• 01-10-2008
kcpilot
mea culpa!!