Which of the following is closest to 10^170 – 10^30 ?  Choose the most appropriate option.
A) 10^210 B) 10^180 C) 10^170 D) 10^90 E) 10^6
10^170 – 10^30   10^30 * (10^140 – 1)   as we know 10^2 - 1 means 100-1 and we get 99, which is approximately 100. hence (10^140 – 1) would remain as 10^140.   and 10^30 * 10^150 = 10^180. Answer is 10^170.
<result>C</result>
Which of the following is closest to 10^170 – 10^30 ?