توضیحات:

We are not used to do quick mental calculations, since we have several electronic devices which can do this for us. Electronic devices are very useful for everyday life, but indeed they made our minds lazy. Sometimes, we haven't got an electronic calculator, so we need to do calculations mentally. This app is a key strategy to live above our targets. Computing ability is not in our nature, but thanks to a correct training, it can be developed. Scroll the question mark and choose the right math symbol. Touch and hold light bulb to get the answer.