# Lecture 1.4 and Workshop 1.5

This is the 3rd lecture of the year, which was followed by an hour’s gap and then a workshop.

The lecture was about subtraction. Many students, but not all of them, were going through lecture questions quite quickly, and then doing workshop questions too.

One noteworthy thing was showing how BODMAS is wrong (or misleading), by doing example 10–5+3. When asked (“I assume most of you have heard of BODMAS or similar. So using BODMAS, should we add or subtract first? Raise left/right hand as appropriate”), majority of students said you should add first. To make it convincing, I also demonstrated with calculator.

Another observation is that attendance at the lecture dropped to 70%. First two lectures had high attendance, at around 90–95%.

Third observation is questions in which one needs to determine if an adjustment is needed after subtracting, to include or not include endpoints. E.g. “How many numbers are in this list: 20,21,22,…,38,39,40?” Many students got it wrong — hopefully they remember this and think about it, but that is unlikely.

I went through material quickly, so ended up going through 1+1–1+1–1+1–1+1–1…. I do not know what people thought — I ought to ask. In future, I think I ought to introduce “rate of change” notation in lecture and go through examples myself, instead of doing it only on the workshop.

Next comes the workshop. Main thing to notice is that a dozen students worked through everything and wanted their work marked so they could leave. Seems a bit of a waste of staff time focussing on these students. Future we will just say that students just need to demonstrate they have made a good effort on all the questions, and they can leave. They can check answer for themselves, and can email me if they want their written work checked.

Some other things worth noting. As expected, rate of change terminology not clear to some students. Question with boxes, some students did not find all possibilities, only one. Problem with masses and scales — students did not understand last part and many did not bother trying. One group did though, and they did an excellent job. (Turns out I never truly understood it!). Lastly, calculations in base 6 got some interesting attempts and responses. Obviously not easy for many students, but I think it is a useful exercise. I actually may make it part of the syllabus in future years as it is a good way to see test “resilience”.