Long Multiplication & Division

To multiply by a two-digit number, break it into place-value pieces and add the parts.

Worked example. $234 \times 12$. Split the $12$ into $10 + 2$:

Division shares a total into equal groups. $864 \div 6$: how many sixes fit? $6 \times 100 = 600$, leaving $264$; $6 \times 40 = 240$, leaving $24$; $6 \times 4 = 24$, leaving $0$. So $864 \div 6 = 144$.

Estimating first keeps you safe: round to the leading digits, e.g. $412 \times 19 \approx 400 \times 20 = 8\,000$, so an answer near $8\,000$ is sensible.