The abacus is as useful and effecient a machine today as it was when it was first created centures ago. Whether you're an expert in the latest computer technology or you're mastering arithmetic and word problems for the first time, it won't take long to learn the basics (and even the not-so-basics) of adding, subtracting, multiplying, and dividing on this ingenious and fun-to-use mathematical tool.
还没人写过短评呢
还没人写过短评呢