Is estimation the best way to solve such problems??

beater wrote:(6.804)^6 (1.701)^-13 / (2) ^19(3.402) ^-7

A. 0.8502
B. 1.0000
C. 1.7010
D. 3.4020
E. 6.8040

There are a couple of reasons why estimation could lead you to the wrong answer here- a couple of answers are close together, and the quantities aren't easy to estimate. If it's a GMAT question, you can be pretty sure you're going to have a lot of simplification- it must be easier than it looks. If you notice that 4*1.701 = 6.804, and 2*1.701 = 3.402, there's a lot of cancellation:

(6.804)^6 (1.701)^-13 / (2) ^19(3.402) ^-7

= (6.804)^6 (3.402) ^7 / (2) ^19 (1.701)^13

= [ (2^2 * 1.701)^6 * (2 * 1.701)^7 ] / [2^19 * (1.701)^13 ]

= [2^12 * 1.701^6 * 2^7 * 1.701^7] / [2^19 * 1.701^13]

= (2^19 * 1.701^13)/(2^19 * 1.701^13)

= 1