Question

what is the estimated product of 43x36

Answer 1

First, we see what numbers we get from rounding down and up 43 and 36:

$\begin{gathered} 43\Rightarrow40\text{ rounded down} \\ 36\Rightarrow40\text{ rounded up} \end{gathered}$

Then, we calculate mentally 40x40=1600, therefore, the estimated product of 43x36 is 1600