(a)[1]
Express $340\,000$ in standard form, giving the answer in that notation.
(b)[2]
Evaluate $\dfrac{4 \times 10^7}{8 \times 10^{21}}$, and present the result in standard form.
(c)[1]
Find $k$ from $7 \times 10^a - 3 \times 10^{a-1} = k \times 10^a$.