Delta Math has incredible sets for seeing volume of cross-sections and solids of revolutions. If you instruct your students to click on “show solution“, they can pull a slider to see the region become a solid! For the cross-section set, it shows the shape (square, rectangle, or triangle) growing along the base. For the disks, it includes the radius with the 3D shape. The washer set shows the washer inside the 3D shape. There is also a matching set, where students can practice matching up the 2D region with a resulting 3D shape, and vice versa.

The five sets I use are in the image below. I have also included videos of the volumes being created when you drag the slider so you can see how cool it is! Delta Math is free for teachers!

Edited: I finally updated my Delta Math post. I love having a website that helps my students AND is so good that THEY ask me for it. It’s the best! Enjoy!

We are now into Week 2 of the Blogging Initiative, “My Favorite”! You should definitely check it out if you would like some blogging inspiration! It is only four posts and it’s not to late to join in.

My favorite for the week is Delta Math, a free online math practice program with problems ranging from middle school to pre-calculus. The amazing Mattie Baker presented Delta Math as one of his favorites at TMC15 last summer. You can watch his presentation at the bottom of this post.

I rarely use Delta Math for daily homework assignments. Instead, I use it to review those basic Algebra 1 skills that many students have either forgotten or did not master during their Algebra 1 year. I give these basic practice sets well in advance of the corresponding Algebra 2 topic that I will be covering in order to get them prepared. I assign one “Problem Set” of about 5 – 10 problems a week. I also give a variety of problem types in the problem sets. Students are able to rework each problem until they get it correct, meaning that they are able to receive full credit on their problem set each week with just effort.

The students can see fully worked out examples of each problem and even watch videos for some problem sets.

I love the explanations on Delta Math, as they usually use methods that I teach in class, like the “box method” for multiplying polynomials. They even color coded the diagonals!

Occasionally I will assign a Delta Math set for homework. For instance, they have some fantastic practice sets for graphs, such as the one for finding domain and range visually.

Delta Math gives you amazing student data. You can see which problems students missed and even their incorrect answers. If I see many students struggling on a set, then I will usually reassign that set in the coming weeks. You can even see how long students took on EACH problem!

How I Use Delta Math:

I assign about 10 review problems per week, due every Tuesday at 8:00 AM.*

I usually require 1-2 of each kind of problem, with a “1 off” designation. This means that they can miss one problem without penalty, but if they miss more than one in a row, they go back to zero.

I assign Algebra 1 problems well in advance of the corresponding Algebra 2 topic.

I assign problems on a spiraling basis where problems increase in difficulty each week. I am staring rational functions in about a month, so next week I will start assigning them basic fraction problems. Next, I will assign them fraction problems with x in them,…

I hold help sessions the day before their problem sets are due for my students that struggle recalling their Algebra 1 skills.

*This biggest drawback is that students forget to do their Delta Math since it is an online program and only assigned and checked once a week. Moving the due date from Monday to Tuesday helped tremendously with this. I also love the Tuesday due date as opposed to Friday as some students wait until the last day to complete it and they are usually pretty wiped out by Thursday night. I use Remind to remind them and mention it in class.

Bonus! Delta Math now has a Delta Math Plus, where students can watch videos for each topic. There is a fee for Delta Math Plus.

Optional Summer Assignment:

Another way I use Delta Math is that I give all rising Algebra 2 students at our school an optional summer assignment on Algebra 1 topics in order to help them refresh their basic skills. I assign just one question per topic, but students can do as many questions as they like.

My students really love Delta Math! Here is some of what they said in my last course survey.

Having Delta Math for homework helped me a lot because it showed me how to do the problems so that when I did a problem similar to the previous, I would know how to do it with a lot more confidence.

Start doing more Delta Math.

Do More Delta Maths.

Do Delta Math – It helps a lot!

Do the Delta Math (this will definitely help)!!

Delta Math was very helpful.

Please give more Delta Math assignments.

I think continuing to assign Delta Math would be wise.