sir plz help in how to find log and antilog values frm the tables?

Asked by Viresh Mohan | 16th Feb, 2014, 02:20: AM

Expert Answer:


1. Let's suppose you want to find the log of 72.98.

Characteristic = 1   (2 digits before decimal. therefore, 2-1=1)

For mantissa, read from the table a number 7298. From the rows, choose 72, and read off from the number under the column 9. The number given in the log tables is 8627. Now read, in the same row, the mean difference under 8. This number is given as 5.

Mantissa = 8627 + 5  = 8632

Thus log 72.98  = Characteristic of 72.98   +   Mantissa of 72.98

                       = 1   +   0.8632

                       = 1.8632

 

2. Find the log of 500.2.

Characteristic = 2   (3 digits before decimal. therefore, 3-1=2)

For mantissa, read from the table a number 5002. From the rows, choose 50, and read off from the number under the column 0. The number given in the log tables is 6990. Now read, in the same row, the mean difference under 2. This number is given as 2.

Mantissa = 6990 + 2  =  6992

Thus log 500.2  = Characteristic of 500.2   +    Mantissa of 500.2

                       = 2   +   0.6992  

                       = 2.6992

 3. Find the log of 0.0009887

Characteristic =  -4 (As there are 4 zero in the given number with decimal, the characteristic is -4).

For mantissa, read from the table a number 9887. From the rows, choose 98, and read off from the number under the column 8. The number given in the log tables is 9948. Now read, in the same row, the mean difference under 7. This number is given as 3.

Mantissa = 9948 + 3  = 9951

Thus, log 0.0009887 = Characteristic of 0.0009887   +   Mantissa of 0.0009887

                             = - 4   +   0.9951

                             = - 3.0049   ( The log of 0.009887 is also written as  .9951, although 
                                                 its value is  - 3.0049 )

Answered by  | 17th Feb, 2014, 12:19: PM

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