11. 17, 200 written in scientific notation is 1.7 x 10^5
21. 0.00105 written in scientific notation is 1.05 x 10^-3
are these correct?
11. 1.72*10^4
10,000 is 10^4
you only have to move the decimal point 4 places to the left to get a number less than 10.
21. correct