Question

The length of a rectangle is measured as 370 mm correct to 2 significant figures. a) What is the upper bound for the length? The width of this rectangle is measured as 19.4 mm correct to 1 decimal place. b) What is the lower bound for the area of the rectangle?​

Answer 1

Answers: a) 375mm b) 19.35

Think of bounds as the most a number can possibly be stretched to still give you a desired result. Up to, but not including, 375mm would still round down to 370mm (that is as far as the number can stretch, up). That is therefore the upper bound. The lower bound would be 365mm, as that is as low as you can possibly go whilst still rounding up (as low down as we can stretch it.)
Using this logic, we can work out any bounds. 19.35 is the lowest we can go, and 19.44999999 recurring is the lowest, so we can go up to, but not include, 19.45.