My little sister which is in 4th grade is struggling to keep up with her classmates at math. Can you please find ways for me to teach her?

Do you know what specific areas she has trouble with? For example, fractions, geometry, algebra, etc. Has a parent had a conference with the teacher to discuss the concern?

Can she bring home her math book from school so that you can work with her on the lesson she had in class that day? There are likely practice tests in the books to use or perhaps her teacher can send home extra practice pages.

Once you know the areas she has difficulty in, you could also find sites online that will help support her learning through activities and games. There are many sites that will allow you to print worksheets as well for additional practice.

If you have something like an iPad, there are numerous free apps that can be used as well.

If she is struggling quite a bit, she may find going back to some lower grade level work and getting a better foundation helps, then work up to what is at her grade level.

Does she know her times tables? When I taught school, the students who struggled the most in math had never learned them.

And what is mom and dad doing to try to help also

It's important that children and adults for that matter, free up their working memory so as to have enough memory available for complicated tasks. If you are too intent on trying to master the 'small stuff' (multiplication for example) then you have very little left over to apply to the actual problem.

It makes sense to me, so I agree with Wondergirl, learning multiplication tables would be very good place to start when it comes to children and maths.

Tut

Another area to look at is her reading. Once into the intermediate grades, reading will become a greater requirement of every subject area, including math.

Some students do well with straight computation, but will have great difficulty when having to determine what steps to take in higher order thinking and/or when there is reading involved. That can be with something such as word problems or simply with reading and comprehending the directions and examples.

Having been a 4th grade teacher for 15 years, I can say that there are a few areas that need to be looked at when a student is struggling. First, is reading level. What grade level is your sister capable of understanding? Textbooks are written in such a way that students who are not reading at a 4th grade level and beyond will not comprehend them. Second, as Wondergirl said, multiplication tables should already be memorized. Not knowing all the way through the 12's will prevent all understanding of 4th grade math concepts, including division, fractions, probability, and of course, multiplication. She should also know her addition and subtraction facts. All of these should be practiced often using flash cards. Third, is your sister studying? 4th grade is the time called upper elementary. There are tests to study for beyond weekly spelling tests. Have her bring her textbooks home every day and weekend. Make sure she reads ahead. 4th grade is a tough transition, and she needs to work hard to stay ahead in all subject areas.

Oh, actually my little sister got to keep up cause we had tutors over the summer, a lot, she managed to stay in school for fifth grade and she kept up but thanks for the advice:)