Answer:
643,000
Explanation:
For n, an integer greater than or equal to zero, 10^n is the same as a 1 followed by n number of zeros.
For example, 10^0 = 1 (1 followed by zero zeros.)
For example, 10^4 = 10,000 (1 followed by 4 zeros)
In your problem you have 6.43 * 10^5.
10^5 = 100,000 (1 followed by 5 zeros).
Since you need to multiply 6.43 by 100,000, just move the decimal point 5 places to the right.
6.43 * 10^5 = 6.43 * 100,000 = 643,000