GRE Math : How to subtract complex fractions

Example Questions

Example Question #11 : Complex Fractions

Simplify the following:

Explanation:

This problem merely requires careful working out of each part. Begin by simplifying the first fraction:

The numerator will be:

The denominator will be:

Thus, we have the following fraction:

Remember that you must multiply the numerator by the reciprocal of the denominator:

Now, work on the second fraction:

This fraction is much easier. After simplifying the numerator, you get:

This is the same as:

Thus, we come to our original expression! It is:

The common denominator of these fractions is . Thus, you have:

Example Question #601 : Arithmetic

Quantity A:

Quantity B:

The relationship between A and B cannot be determined.

The two quantities are equal.

Quantity B is greater.

Quantity A is greater.

Quantity A is greater.

Explanation:

As it is, quantities A and B have different denominators, so making a comparison can be tricky. Making a common denominator will allow for comparison of just the numerators, so that would make a good first step:

Quantity A:

Quantity B:

Disregarding equal denominators, since they'll always have a positive value, compare the numerators. If  is subtracted from quantity A and from quantity B, we're left with  for the former and  for the latter.

Quantity A is greater.

Example Question #11 : Complex Fractions

Quantity A:

Quantity B:

The relationship between A and B cannot be determined.

Quantity B is greater.

Quantity A and Quantity B are equal.

Quantity A is greater.

The relationship between A and B cannot be determined.

Explanation:

One way to approach this question is to try to reduce the complexity of each quantity. By subtracting the value of Quantity A,  from both A and B, we can make a new comparison:

Quantity A':

Quantity B':

Now, it's easy to see that for different values of  Quantity B may be greater, lesser, or equal to Quantity A.

Since  is not restricted in its possible values, the relationship cannot be determined.

Example Question #14 : Complex Fractions

Rhoda can prune  rhododendrons in  hours, while Rhonda can prune  in  hours. If a work day is  hours, how many rhododendrons will Rita have to prune per hour so that the team prunes the garden's  rhododendrons?

Explanation:

To find out how many rhododendrons Rita will need to prune in an hour, we must first find out how many she needs to prune.

If Rhoda can prune  rhododendrons in  hours, then she can prune  in  hours, and if Rhonda can prune  in  hours, she can prune  in  hours.

If this is not readily apparent, it can be found by finding out how many each prunes in one hour, then multiplying by .

Rhoda:

Rhonda:

Between Rhoda and Rhonda,  of the  rhododendrons can be pruned, leaving  for Rita.

Since she has  hours for the task, her rate of pruning can be found to be: