Explanation:
5⁴×5² = 5⁶
10⁶/10³ = 10³
so, we have 5⁶/10³ = 15.625
and in scientific notation we have to write the first digit (which is not 0) in front of the decimal point, and the following digits of the number as pairings after the decimal point, and then indicate a multiplication with a power of 10 to tell us the right position of the decimal point in the plain number.
so, 15.625 as plain number is
1.5625 × 10¹ in scientific notation.
therefore option 1 is correct.