Rounding of numbers – one of the simplest transformations in the mathematician for whose performance the sharpness is necessary. And constant trainings in this area will allow to perfect the received skill to perfection.
1. Remember the rule of rounding. It considerably will simplify process of understanding of actions. In fact, rounding – transformation of number towards integration of the category, its reduction to a certain look. Similar operations are performed for simplification of calculations if, for example, it is necessary to find approximate value, and the lack of units in calculations is not critical. According to the rule, the figure of the serial category remains invariable in case directly behind it is 1, 2, 3, 4 and, naturally, 0. It is possible to correct safely them on zero. The number terminates on 5, 6, 7, 8 or 9 – to digit figure it is necessary to add 1.
2. Define category figure by logical substitution. Any integer comes to an end on units, then dozens, hundreds, thousands, etc. (from right to left) follow. Therefore, dozens are ranked as the second order, and units will be necessary for commission of action of rounding. Other figures will not affect the end result in any way therefore they can be rejected mentally.
3. Make rounding to dozens on the following algorithm: • Remember value of units; • Replace an indicator of the second category if behind it there are figure equal 5 or more it, and leave former in other cases; • Put "0" instead of unit; • Write down the received result. For example, it is required to round number 17983 to dozens. As the border of transformations is on the second category (dozens – the second figure on the right), about everything that is present to the left of "8", it is possible to forget for a while. In the status of units there is "three". Its value below "5", therefore, figure of the category does not change, and instead of "3" "0" appears. Thus, at the exit number 17980 turns out. It is also final result. If number 7605 is planned to round to dozens, then it is necessary to act this way: • To replace figure of the category "0" with "1" (0+1=1); • Instead of "5" to write "0". As a result number 7610 turns out.