Question

write the following number in scientific notation. 0.000000721
$7.21 \times 10^{7}$
$7.21 \times 10^{-6}$
$7.21 \times 10^{-7}$
$7 \times 10^{-7}$

Explanation:

Step1: Move decimal to 1-10 range

Shift decimal 7 places right: $0.000000721
ightarrow 7.21$

Step2: Determine 10's exponent

Decimal moved 7 places left originally: $10^{-7}$

Step3: Combine into scientific notation

$7.21 \times 10^{-7}$

Answer:

C. $7.21 \times 10^{-7}$