Question

What is 0.00000000472 estimated as the product of a single digit and a power of 10?

Answer 1

$0\underbrace{.000000004}_{9\to}72=4.72\cdot10^{-9}$

Answer 2

The power of 10 is equal to the numbers of 0;
$10^{-9} *472 = 4.72*10^{-11}$  ≈$5* 10^{-11}$

Final answer: $5* 10^{-11}$