Click on slider a and assign for it the value a = 0.5, then one of the blocks, representing tens, will jump from left to the right side (the side of ones). Click on slider i, and assign for it the value i = 0.25. The simulation of the above model is a resemblance of the mental process for subtracting two 2-digit numbers. After the transfer block is decomposed in 10 equal rectangles is possible to perform the subtraction operartion. The new situation of 3 blocks and 13 rectangles allows us to find the difference between the two sets of blocks and the difference between the two sets of rectangles. The result is 2 blocks and 7 rectangles which represent 2 tens and 7 ones, respectively. There are two black curtains (represented by black rectangles) on GeoGebra window which are used to cover the blocks and the rectangles that are taken away during the subtracting process.
