When writing this post it’s Easter time. One thing to do during the Easter is to learn how to solve a Rubik’s Cube. A year ago my daughter learned to solve the 3x3x3 Rubik’s Cube, and we just played with it again this week. A lot of people think solving the cube is cool but difficult and are impressed. At the end of the day solving the cube is not difficult, it just takes a few days of hard work. Here is a quick overview to get you started, and at the end of this blog post I have included a video of my daughter solving the cube.
The photos is lisenced under a Creative Commons Attribution-Noncommercial-Share Alike 3.0 License
You could use several different strategies when solving the 3x3x3 Cube. Strategies like ´Layer by Layer´, ´Block´ and ´Corner first´ all have variations with different methods. I think the easiest way is to use a ´Layer by Layer´ approach. This strategy is a good solution for beginners. If your goal is to do speedcubing and try to set a world-record, then you need to apply a faster method. Here you can read more about the history of the Cube and different strategies for solving it. If you start searching a lot of the stuff are heavy mathematics and algorithms etc. It’s easy to get all sweaty and discouraged, but I just skipped the nitty gritty stuff and just set some ambitions for us to learn how to actually solve it – in an easy way.
So going for the easiest solution to learn a kid we focused on the Layer by Layer approach. Applying the layer method we solve one layer at a time. We first solve one side of the cube (typically the top layer), then the middle layer, and finally the last layer. Different strategies within the layer method exists and it is possible to optimize towards speed. Typically some guides use a method where you solve the final edge pieces at the end other solves the corners as the last step. I am using the approach where the last thing I do is to solve the corners.
Solving it step by step could be done in seven steps:
- Solve the cross on first layer
- Solve the corners on first layer
- Solve middle layer
- Solve the cross on the last layer
- Place the cross on the last layer correctly
- Place the corner pieces on the last layer correctly
- Solve the corner pieces on the last layer
To solve it you need to learn the move notations. It seems that most Cube enthusiasts use a notation developed by David Singmaster. But for solving the Cube using the method in the link above you just need to memorize the following move notations:
- R = Right Face – right side of the cube
- L = Left Face – left side of the cube
- U = Up Face – Top side of the cube
- D – Down Face – Bottom side of the cube
- F = Front Face – Front side of the cube
- B = Back Face – Back side of the cube
A letter with an “i” after it means an inverted or counter-clockwise move when looking at the face directly. If the algorithm says F, then you should turn the front clockwise. If the algorithm says Fi then you should turn the Front counter-clockwise. The solutions guide is pretty easy stuff, and all the moves are explained visually.
Everything is explained in the solutions guide, but I’ll walk through how I solve it because I have simplified it a bit, and also doing it in a bit different order than the guide.
When I learned my daughter the cube last year, she did not use algorithms for the first two steps. The first two steps is so logical that you can do it without the algorithms. Then I wrote the algorithm for each step on a piece of paper, and we worked to memorize and train it step by step. The algorithm kind of became a rhyme. I translated the algorithm into my own language, which is Norwegian. From there it was just fun and a game trying to remember each step.
1. Solve the cross on first layer
The first step is to get a cross. Just pick whatever side you feel for. Remember that the colors must match. The Edge piece colors match the top center piece and the side center pieces.
The algorithm to be used are:
2. Solve the corner pieces on first layer
When you have the cross, then it is time to complete the corner pieces on the top layer.
The algorithm to be used are:
3. Solve middle layer
Great, now you can start solving the next layer. I find it easier to turn the cube upside down now. The first layer solved should now be at the bottom.
The algorithm(s) to be used are:
Here is where I have just skipped the last algorithm, just to make it easier for my kid (and my self) to remember. One algorithm less to memorize. The drawback is that it often will take more moves. The first algorithm is used to move the edge piece down towards the right. The second algorithm is used if you need to move the edge piece down and towards the left. If you skip one of the algorithms and memorize only one of them, then you might have to repeat the algorithm three times. Lets walk through an example. If the blue color is facing towards you (front) and the red color is on the right side you need the blue/red edge piece. If the edge piece is placed in the starting position (see the guide) with the blue color facing towards you and the red color on top then you can use the first algorithm once to get it in the correct spot. But if it is twisted, facing its red side towards you and the blue color on top, you need to repeat that algorithm three times. The first time will put the edge piece at correct spot but it is flipped. So using the algorithm once more you will move it back on top (actually it will land on a different place on top) but now it is flipped and the blue color will be facing towards you. Use the algorithm for the third time and it will be correctly placed. A bit more job, but you only need to memorize one and not two algorithms.
Now you should have a cube with to layers solved. Cool! Time to solve the last layer.
4. Solve cross on the last layer
Now it is time to make a cross on the last layer (pretty much the same as you did on the first layer). As you can see from the guide, it is possible to optimize here using different algorithms. I have chosen to just memorize one algorithm and repeat that algorithm until I get the cross. Playing with it you will learn how to position the cube to get the cross.
The algorithm to use is:
I use a different procedure than they guide now and solves it in a slightly different order. Let’s walk through how I solve it from here:
5. Place the cross on the last layer correctly
Sometimes you get lucky and the cross is correctly placed. But if it is not, you need to move the edge pieces to the correct side of the cube.
The algorithm to use is:
6. Place the corner pieces on the last layer correctly
By now you have only four corner pieces left and the Rubik’s Cube is solved! So, first you need to check if the corner pieces are placed correctly. If not, you need to move them. As you can see from the photo below, the colors on the corner pieces should match the three sides. The corner pieces could very well not be solved correctly but that is something for the next step to deal with.
The algorithm to use is:
7. Solve the corner pieces on the last layer
Almost there! You only need to twist the corner pieces to finish the cube! Be sure to keep the corner piece that you will solve at your right thumb – the corner facing towards you at the right side. Repeat the algorithm until the correct color is on top. This last step is very easy but also has a tricky move. If you need to solve more than one corner piece, you need to rotate the top layer after finishing a corner. Rotate the top layer counter-clockwise so that you get a new corner piece ready to go through the algorithm.
The algorithm to be used is:
Finally.. here is a video of my kid solving the Rubik’s Cube using the approach described above. Kids really love the cube and be able to actually solve it is a great experience for them!