Rounding, Estimation and Bounds: Where to start

Nobody measures a plank to the last millionth of a millimetre. The forty-five centimetres written on it is a rounded number, and the true length sits somewhere close by. This chapter is about that gap. First you round a number well. Then you use rounding to check a calculation. Then you find how far the true value could be from the one you were told. So the right first video depends on which of those three jobs you need.

The chapter climbs in that same order, so the early videos hold up everything after them.

If significant figures and decimal places still blur together, start with Rounding to significant figures and decimal places. Every course sets it. One examiner's report records students rounding to one significant figure as if the question said one decimal place. Estimating a calculation by rounding comes next. In a question, estimate means round every number first, then do the sum with the rounded numbers. The mark is lost when the exact answer is worked out instead, with no rounding at all. If you can already round and estimate, go straight to Upper and lower bounds of a rounded value. It finds the smallest and largest a rounded number could really have been. It also covers truncating, which means cutting digits off instead of rounding, and one examiner's report describes students treating a truncated value as if it had been rounded. Bounds of a calculated result is for Higher tier only. It takes two rounded measurements, such as a distance and a time, and chooses which bound of each to use. If you sit Foundation, leave it out, because nothing after it depends on it. Error intervals from rounding and truncation writes the two bounds as one inequality, with the right sign at each end. Truncated numbers catch people out here, because the interval sits on one side of the number only. Limits of accuracy: upper and lower bounds finishes the chapter. It picks the bound that answers a real question, such as whether a shelf will fit a gap. Every title and every code on this list works as a search. The quickest place to use it is the scholafly.com website, which indexes every video in every subject.

Next in the chapter is Rounding to significant figures and decimal places. Hopefully that's next in your feed, but if not, search for ScholaFly M A oh seven, oh one.

Every other video is on scholafly.com too, easy to search by video code or by keyword. Whatever you're revising, go there and have a look, or, watch the next video.