### Instruction: Compute without using a calculator: $42!/40!$.### Response: I know that $42!$ means $42 \times 41 \times 40 \times 39 \times ... \times 1$, and similarly for $40!$.
So, to find $42!/40!$, I can cancel out the common factors of $40!$ from both the numerator and the denominator.
This leaves me with $42 \times 41$ in the numerator, and $1$ in the denominator.