Question

Write $840$ in prime factorisation form.

Answer 1

$$\begin{gathered} 840=2\times 420 \\ 840=2\times 2\times 210 \\ 840=2\times 2\times 2\times 105 \\ 840=2\times 2\times 2\times 3\times 35 \\ 840=2\times 2\times 2\times 3\times 5\times 7 \end{gathered}$$

Therefore, prime factorisation of $840=2\times 2\times 2\times 3\times 5\times 7$.