21.78*10^-6 in standard form.

Answer

2.178 x 10^-7

Step-by-step explanation:

You can only have one number to the left of the decimal. 21.78 x 10^-6 has 2 numbers to the left of the decimal. To make it standard form move the decimal left one, and add that value to the - 6, in this case that would add a - 1. That makes it 2.178 x 10^-7.