1.

If `log_10 7=0.8451,` find the position of the first significant figure in `7^-20.`A. 15B. 20C. 17D. 18

Answer» Correct Answer - C
`"Let" x = 7^(-20)`. Then,
`"log"_(10) x = -20 "log"_(10)7 = -20 xx (0.8451) = -16.9020`
`"log"_(10) x = -17 + 1 - 0.9020= bar(17). 0980`
Hence, position of first significant figure is 17 th.


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