example: 47 has been rounded to the nearest cm, find the greatest and least possible values of the actual measurement
46.5 ≤ x < 47.5
example: a student weighs 73kg, their weight has been rounded to the nearest kilogram, find the greatest and least possible values of the actual measurement
72.5 ≤ x < 73.5
example: find 18.7g to the nearest 0.1g
18.65 ≤ x < 18.75