Limits of accuracy: upper and lower bounds
A rounded measurement is really somewhere in a range. Draw the range, then use the bounds to find the biggest and smallest answers.
- روسيا: الصف ٩
- بريطانيا: السنة ١٠
لم يُترجَم هذا المختبر إلى هذه اللغة بعد.
الدليل
A length of 7.3 cm to 1 decimal place has been rounded. The real length could be a little below 7.3 or a little above it.
Half of the rounding step goes each way. To 1 d.p. the step is 0.1, so the length is from 7.25 up to, but not including, 7.35. We write ٧٫٢٥ ≤ x < ٧٫٣٥: 7.25 is the lower bound and 7.35 the upper bound.
The lower bound is included because 7.25 itself rounds up to 7.3. The upper bound is not, because 7.35 rounds up to 7.4. On the number line the lower end is a filled dot and the upper end is a hollow dot.
When you calculate with rounded numbers, use the bounds. The biggest area uses the biggest sides. The smallest difference takes the smallest first number and the biggest second number.