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Question 20

Round up the following upto three significant figures:
(i) 34.216
(ii) 10.4107
(iii) 0.04597
(iv) 2808

Answer

Rounding off a number means that the digits which are not significant have to be dropped.The rules are as follows:

  1. if the digit to be dropped is more than 5, then add 1 to the preceding significant figure.For eg in the number 11.06, the digit to be dropped is 6.Therefore the preceding digit 0 is increased by one & the final result is 11.1.
  2. if the digit to be dropped is less than 5,then it is deleted as such without bringing any change in the preceding significant figure.For eg 43.123 is to reported upto four significant figures,then the last digit 3 is dropped & the final answer is 43.12.
  3. if the digit to be dropped is 5 then the preceding significant digit in the number may be left unchanged if it is even & may be increased by 1 in case if it is odd.Eg 1.6145, if reported upto four significant figures will become 1.614 after rounding off. Similarly 1.6175 will become 1.618.
  4. if during rounding off, more than one digit is to be dropped form a particular number, then they are dropped on at a time by following the above rules.

(i) 34.2

(ii) 10.4

(iii) 0.0460

(iv) 2810

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