add by adding
Possible reasons: To add or subtract fractions, To compare fractions with different denominators.
Fractions in decimal form are easy to compare and to add and subtract from one another.
I am not entirely sure what you mean, but if you need to add, subtract, or compare two fractions, they need to have the same denominator.
You DO need a common denominator to add, subtract, or compare fractions. You DO NOT need a common denominator to multiply or divide fractions.
To compare two fractions, convert them to a common denominator.To compare two fractions, convert them to a common denominator.To compare two fractions, convert them to a common denominator.To compare two fractions, convert them to a common denominator.
Two ways: convert them to decimals or convert them to similar fractions and compare the numerators.
you compare them
You can compare similar fractions by looking at their numerators. You can compare dissimilar fractions by converting them to similar fractions and looking at their numerators. You can convert a dissimilar fraction to a similar fraction by finding the least common denominator.
it stay the same when you subtract fractions and when you add fractions.
you have to compare the common fractions
You can either convert fractions to decimals and compare the decimal numbers; find equivalent fractions with the same denominator and then compare numerators or find equivalent fractions with the same numerator and then compare denominators.
The first step, to add, subtract, or compare fractions, is always to convert the fractions to equivalent fractions, that all have the same denominator. You can use one of several techniques to get the LEAST common denominator, or simply multiply the two denominators to get a common denominator (which in this case may, or may not, be the smallest common denominator).