#math/mental For **two-by-one multiplication** the trend continues. We go left to right and solve the problem sequentially. This time the loop is multiply add multiply add etc. Consider $42\times 7$ $ \begin{align} 42\times 7 & \text{ is} \\ 280+14 & \text{ is} \\ 294 \end{align} $ The $2\times 7=14$ is calculated in the same breath. Eventually $42\times7$ will be as well when we do larger problems. The last digit multiplication only has two possibilities. One, it results in a single digit like $74\times 2=14\textcolor{#1f9d57}{8}$. Second, it results in two digits like $ \begin{align} 76\times 2 =1\textcolor{#1f9d57}{4} & 0 \\ +\textcolor{#1f9d57}{1} & 2 \\ \hline 15 & 2 \end{align} $ . While saying "one-hundred" we should be looking ahead and seeing if we are case one or two. That way we quickly say "forty" or "fifty" in that same breath. --- $ \begin{array}{ccc} \begin{array}{r} 38 \\ \times\ 9 \\ \hline \end{array} & \qquad \begin{array}{r} 67 \\ \times\ 8 \\ \hline \end{array} & \qquad \phantom{000} \\[25pt] \phantom{000} & \qquad \phantom{000} & \qquad \phantom{000} \\[25pt] \phantom{000} & \qquad \phantom{000} & \qquad \phantom{000} \\ \end{array} $