First example:
A wheel has a diameter of 82 cm. What is its circumference?

A typical example of an incorrect answer:  the use of 3.14 and thinking that 82 cm is an "exact" measurement.

Or correctly rounding the answer with 3 digits (Round "0" rounds to units), but using 3.14:

The correct answer:

Second example:
A school class in a winter month detects the outside temperature on each school day at 9 o'clock:

               

I round to tenths:

Third example:
Unlike the behavior of pocket calculators, the computer operates with numbers in a somewhat different way, so the results of the operations may differ by a few units on the last (the 17th) digit.  However, they are more digits than are usually needed. With this calculator we can round numbers.  Some example.
1 / 3 = 0.3333333333333333
10 / 3 = 3.3333333333333335
3.3333333333333335 round to 14^ digit after units: 3.33333333333333
3(-8)
-8 ^ 0.3333333333333333 = -1.9999999999999997
-1.9999999999999997 round to 15^ digit after units: -2


Let's compare the values of these two numerical terms: (19/6177)^2 and (10119/355 - 12398/435)^2.
19 / 6177 = 0.0030759268253197345
0.0030759268253197345 ^ 2 = 0.000009461325834721535
10119 / 355 = 28.504225352112676
12398 / 435 = 28.501149425287355
28.504225352112676 - 28.501149425287355 = 0.003075926825321318
0.003075926825321318 ^ 2 = 0.000009461325834731285

Only 11 digits are equal while the two terms are equivalent. Similar problems also happen with the usual calculators. Let's see how we could check the equivalence of the two terms:
355 * 435 = 154425
10119 * 435 = 4401765
12398 * 355 = 4401290
4401765 - 4401290 = 475

10119/355 - 12398/435 = 475/154425. I can find that:
475/154425 -> 19/6177

Fourth example:
In the input boxes it is possible to put not only single numbers but also numeric expressions. An example: