Question

A cell phone weighs about 2.8X10^n pounds. Which value of n is most reasonable? A)-3 b)-1 c)0 d)1

Answer 1

Just plug in every value and see if it's a reasonable weight for a cell phone.

$\sf 10^{-3}=0.001$
$\sf 10^{-1}=0.1$
$\sf 10^0=1$
$\sf 10^1=10$

$\sf 2.8\times 0.001=0.0028$
$\sf 2.8\times 0.1=0.28$
$\sf 2.8\times 1=2.8$
$\sf 2.8\times 10=28$

So what is the most reasonable weight for a cell phone? 0.0028 pounds, 0.28 pounds, 2.8 pounds, or 28 pounds? I would definitely say 0.28 pounds.

Answer 2

The average cell phone weighs about 4 ounces, or 0.25 pounds... 0.28 is closest to this number.

2.8 * 10^-3 = 0.0028 - Much too light

2.8 * 10^-1 = 0.28 - Reasonable weight

2.8 * 10^0 = 2.8 - Too heavy

2.8 * 10^1 = Much too heavy