what are the operations with rational numbers(fractions)- the rules fro +,-,x and÷. ,give an example?

Answer 1

Mathematical operations have a hierarchy that governs the order in which they apply.

First apply parentheses
Second apply exponentiation "^"
Third apply multiplication and division (equal hierarchy)
Fourth apply addition and subtraction (equal hierarchy)

When two operators have equal hierarchy, apply them left to right.

Answer 2

the rule you should remember for big problems with with multiple operations is this: Please Excuse My Dear Aunt Sally.

P=Parenthesis
E=Exponents
M=Multiplication
D=Division
A=Addition
S=Subtraction

for any problem, you go through beginning with P, before any part of the problem, even if its not on the left side.

Example: 25+(6X6)/2=?
Step 1) you do the parenthesis first, which is 6X6=36
Step 2) then you divide 36 by 2 to get 18(since there is no more multiplication involved in the problem)
Step 3) then you take 18 and add it to 25 to get 43.

i hope this helped!

Answer 3

Addition: a/b + c/d = (a*d + b*c)/(b*d)
Subtraction: a/b - c/d = (a*d - b*c)/(b*d)
Multiplication: (a/b) * (c/d) = a*c/(b*d)
Division: (a/b) / (c/d) = a*d/(b*c)
Equality: a/b = c/d iff a*d = b*c

Just replace "a", "b", "c", and "d" with the numbers from the fractions, and you'll end up with the answer.

Answer 4

It's all here:
http://en.wikipedia.org/wiki/Fractions

Have fun!