One of my Y7 students was working on part 3 of this homework today. We decided to try to accurately measure the weight of a grain of rice, using only a set of electronic kitchen scales.
Of course, we had to do some division and then interpret the results on the calculator too.
...and no, I'm not going to tell you how many there were - other than, a grain of rice doesn't weigh very much at all! Why not carry out the investigation yourself - we could compare results!