Numbers rounding off

If the pressure coefficient is now, or was in an earlier step, 5% uiutei the 0.29 value, calculate a new mean blade velocity using the rounded off number of stages and the original pressure coefficient, 0.29. Use the calculated blade velocity in the subsequent step for compressor speed Calculate the speed. 

We have seen that we must sometimes reduce the number of digits in our calculated result to indicate the accuracy of the measurements that were made. To reduce the number, we round off numbers other than integer digits using the following rules. 

Trained scientists often make mental estimates of numerical answers to quite complicated calculations, with an ease that appears to border on the miraculous. Actually, all they do is round off numbers and use exponents to reduce the calculation to a very simple form. It is quite useful for you to learn these methods. By using them, you can save a great deal of time in homework problems and on tests, and can tell whether an answer seems reasonable (i.e., whether you ve made a math error). 

Once you decide how many digits to retain for your answer, the rules for rounding off numbers are as follows ... 

The temptation to round off numbers before the end of the calculation should be resisted. If all of the calculations are done in a single step this temptation will not present itself because calculators store more figures than the display can show. 

In rounding off numbers, (a) increase the last retained digit by 1 if the leftmost digit to be dropped is more than 5, or is 5 followed by any nonzero digits ... 

In most calculations you will need to round off numbers to obtain the correct number of significant figures. The following rules should be applied for rounding. 

Finally, a rule of thumb for rounding off numbers in which the digit to be dropped is a 5 is always to make the last digit of the rounded-off number even ... 

The following sample study sheet provides a detailed guide to rounding off numbers calculated using multiplication and division. (Addition and subtraction will be covered in the subsequent discussion.) Examples 8.4 and 8.5 demonstrate these steps. 

Sample Study Sheet 8.1 Rounding Off Numbers Calculated Using... 

The following sample study sheet provides a guide to rounding off numbers calculated using addition and subtraction. 

Rounding off - do not round off numbers until you arrive at the final answer. 

If you missed 2, go to Significant Figures and Rounding Off Numbers, page 13. 

Scientific Notation Significant Figures in Calculation of Results Rounding Off Numbers... 

Helpful Hint Refer to the discussion of rounding off numbers on page 20. 

In rounding off numbers, look at the leftmost digit to be removed ... 

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