I won't repeat the good suggestions already made, but I'll add this: find a set of the Open University MST124 text books. The OU publishes their own maths books, which are specially written for self-study (since that's your only option with the OU) and their courses generally assume very little or no previous knowledge. There's an even more basic course (MST123 I think) if that one is too advanced. These are serious courses that form part of their Mathematics degree course so they are very thorough and, I hate this word, but rigorous.
Of course you get the books when you sign up for the course, but it's way cheaper to get the books and study on your own, and you'll get 90% of the information that way.
I don't know if you'll find the pace quick or not; personally I would say that learning maths is very hard, and the materials you use are unlikely to prove to be the botteneck (spoiler: it's you).
I'm studying for a Math BSc with the OU and I think their books are great. They are designed for 100% self-study and are polished over the years. The range of topics in level 1 math courses such as MST124 or MST125 is huge, while keeping the appropriate level of difficulty.
The OU; the Open University. It's a British university founded sixty or so years ago with the intent of widening access to higher education. Their campus is centred in Milton Keynes, a bit north of London.
I took a Masters in Maths with them and it was brutal. Serious exams are a youngster's game. I got a glimpse into why so many Cambridge wranglers were also serious atheletes.
Search for "Open University MST124" or similar on www.ebay.co.uk or www.amazon.co.uk. There seem to be plenty of copies of 124 available on both at the time of writing.
> Question 1: Sara wants to buy a desk before she starts her Open University course. She has chosen a suitable place for it but needs to measure the space before going to buy it.
> Which of these units is the most suitable for measuring the width of the desk? (a) millimetres, (b) metres, (c) centimetres, (d) kilometres.
Seems pretty arbitrary to me. Okay (d) is arguably out. (b) is maybe out? (c) vs (d) seems a toss up to me. Who cares if it's 1234mm or 123.4cm? How is this even a good question? Not a good sign
Note: the answer they want is (a). I don't think I have a tape measure I could get accurate millimeters on especially given measuring a space where I need to bend the tape at 90 degrees like next to a wall.
I might hazard that you, by virtue of being here and by virtue of having dug so far into the question, are exactly not the kind of person this question is targeted at.
Imagine being someone who cannot produce an answer to this question. Who cannot discuss it.
The vast majority of people for whom this entry-level course is aimed at do not think like you. The purpose of the question is not to elicit a correct answer, although I note the effect intended actually worked perfectly on you and the question has been a success in your case. Maybe you are exactly the kind of person this question is aimed at!
The reason for the question, IMO, is not to get the given answer.
The reason is to learn why there is an answer, at which point you can give an opinion as to whether cm/mm are better. You've missed the primary step, and almost certainly are - as others point out - over qualified for this question (which is a precursor to discussions of decimal precision).
Often when helping the kids with homework I find myself answering "well this is the answer they want ... but the real answer is ...".
tl;dr the question is there to make you think, not because there's only one answer.
I have no direct experience of the OU, but I did have a mathematics teacher (head or deputy head I think of the department at a large school, and taught the more advanced courses) who used it.
Not taught courses, took its courses himself, in mathematics.
It went up in my estimations then for sure, because he was already a great teacher, intelligent and knowledgeable in the subject (certainly more than enough for up to 'Further Additional' at A level) and studying for his own interest (or I suppose a career change or further study for all I know).
Of course you get the books when you sign up for the course, but it's way cheaper to get the books and study on your own, and you'll get 90% of the information that way.
I don't know if you'll find the pace quick or not; personally I would say that learning maths is very hard, and the materials you use are unlikely to prove to be the botteneck (spoiler: it's you).