The Work of Two Students Is Shown Below $\begin{array} { l } 732\quad\quad \text { (i) } 8341 \\\underline{ - 245 } \quad \quad \underline{- 4567 }\\513\end{array}$

Essay

The work of two students is shown below. Each student "invented" the method used; that is, it was not taught to the student. Figure out what each student was thinking while doing the problem. Then work the second problem (i) using the same method as the student, and (ii) comment on the student's method in terms of the "number sense" exhibited.
A)
$\begin{array} { l } 732\quad\quad \text { (i) } 8341 \\\underline{ - 245 } \quad \quad \underline{- 4567 }\\513\end{array}$
B) 19 × 35. Well, 20 × 35 is like 10 × 35 two times, so that's 350 two times, which is 700. But that's twenty 35s and I only want nineteen 35s. So 700 minus 30 is 670 minus 5 is 665.
(i) 21 × 43