The number π is used in many formulas. It is one of the major constant mathematical sizes. This constant represents private from division of length of a circle into its diameter. As a result of such division the recurring acyclic decimal decimal turns out. Usually for calculations the number π is rounded with different degree of accuracy.

## Instruction

1. At the solution of tasks where in formulas the number π is used, the absolute accuracy of calculations cannot achieve. Accuracy degree in many respects depends on to what sign after a comma to round infinite decimal fraction including a constant π. The most widespread option — rounding to the 100-th, that is π=3.14.

2. Remember rules of rounding of recurring decimals. It is possible to look at it on the example of the same number π. Not rounded fraction looks so: π=3.14159 … If to round it to ten-thousand shares, then it will turn out that π=3.1416. Pay attention that the figure in the fourth category after a comma is 1 more, than in initial fraction. According to the standard rules of rounding, such increase happens if the number of units of the following category are more or equally 5.

3. From this one interesting property of number π follows. At a recurring decimal decimal 3.14159... in the third ambassador of a comma the category there is figure 4. That is if to round a constant to the tenth, it is necessary to leave the same number, as in initial fraction as 4

4. When rounding to thousand consider that the sign, the fourth after a comma — 5. That is the value of the third category increases in this case by unit and π=3.142.