EK Technique Guide (#4 page 12 of 2nd edition) - Simple Math

[Gauss44]

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Which shortcuts did you use to do this problem? Topics in the chapter include rounding numbers and adding exponents.

4. 1/2(3.4*10^2)(2.9*10^8)^2

A. 1.5*10^18
B. 3.1*10^18
C. 1.4*10^19
D. 3.1*10^19

Correct answer is C.

 

[Sarvish]

(2.9*10^8)^2 ~= 9*10^16

9*10^16*3.4*10^2 ~= 30*10^18 = 3*10^19 (Rounded up in the top, so safe to round down here)

3*10^19 * 1/2 = 1.5*10^19 ~ C

 

[Gauss44]

(2.9*10^8)^2 ~= 9*10^16

9*10^16*3.4*10^2 ~= 30*10^18 = 3*10^19 (Rounded up in the top, so safe to round down here)

3*10^19 * 1/2 = 1.5*10^19 ~ C

Perfect!