4.0 * 10 ^5 * 3.0 * 10 ^3
Multiply the numbers together
4.0 * 3.0 = 12.0
Add the powers of 10
10^5 * 10 ^3 = 10 ^(5+3) = 10 ^ 8
Puth them back together
12.0 * 10^8
Now this is not scientific notation because there is more than 1 number before the decimal
Move it one place to the left
1.2
and add one to the exponet
8+1 = 9
1.2 * 10^9
The answer in scientific notation is
1.2 * 10^9