Try this ACT math practice question on exponents and scientific notation:

Given $a$ and $b$ are positive integers, what is $\dfrac{60 \times 10^a}{3 \times 10^b}$ expressed
in scientific notation?

1. $\quad 2 \times 10^{a-b-1}$
2. $\quad 2 \times 10^{a-b+1}$
3. $\quad 2 \times 10^{(\frac{a}{b}-1)}$
4. $\quad 20 \times 10^{a-b-1}$
5. $\quad 20 \times 10^{a-b+1}$