Answer:
- lower: 20.5 cm
- upper: 21.5 cm
Explanation:
You want the lower and upper bounds for the length if it is reported as 21 cm correct to 2 significant figures.
Bounds
A value rounded to the nearest centimeter is within 1/2 cm of the reported value. That is, for some length x, it will be reported as 21 cm when ...
|x -21| < 0.5 . . . . . . centimeters
-0.5 < x -21 < 0.5 . . . . . unfold the absolute value
20.5 < x < 21.5 . . . . . . . add 21
(a) Lower bound
The lower bound for the length will be 20.5 cm. A value equal to 20.5 cm will be rounded to 21 cm.
(b) Upper bound
A value equal to 21.5 cm will be rounded to 22 cm. 21.5 cm is the upper bound of values that will be rounded to 21 cm.
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