Question

What is 0.0003840 expressed in scientific notation

Answer 1

You can write the fraction 0.0003840 a number of ways.
  0.0003840 = 0.003840/10 = 0.03840/100 = 0.3840/1000 = 3.840/10000

The one we're interested in is the last one, which has one non-zero digit to the left of the decimal point. The power of 10 in the denominator is the 4th power (the number of zeros is 4). 10^4 in the denominator is equivalent to multiplying by 10^(-4) in the numerator.

Expressed in scientific notation,
$0.0003840=3.840 \cdot 10^{-4}$

Answer 2

0.0003840

Written in scientific notation!

Move the decimal point.

.00384 x 10^1

.0384 x 10^2

.384 x 10^3

3.84 x 10^4

38.4 x 10^5