Find the value of z when x = 12.5, a = 0.572 and b = 0.447. Write down your full calculator display.

Write down your answer to part (a)

(i) correct to the nearest 1000 ;

(ii) correct to three significant figures.

Write your answer to part (b)(ii) in the form a × 10^k, where 1 ≤ a < 10, \(k \in \mathbb{Z}\).

\(z = \frac{{17{{(12.5)}^2}}}{{(0.572 - 0.447)}}\)     (M1)

Note: Award (M1) for correct substitution into formula.

= 21250     (A1)     (C2)

[2 marks]

(i) 21000     (A1)(ft)

(ii) 21300     (A1)(ft)     (C2)

Note: Follow through from part (a).

[2 marks]

\(2.13 \times 10^4\)     (A1)(ft)(A1)(ft)     (C2)

Notes: Award (A1)(ft) for 2.13, (A1)(ft) for \(\times 10^4\). Follow through from part (b)(ii).

[ 2 marks]

Many candidates calculated \(\frac{{17{x^2}}}{a} - b\) instead of \(\frac{{17{x^2}}}{{a - b}}\) on their calculators; however they were able to get follow through points. It is important that candidates learn how to correctly input expressions into their calculators.

Many candidates calculated \(\frac{{17{x^2}}}{a} - b\) instead of \(\frac{{17{x^2}}}{{a - b}}\) on their calculators; however they were able to get follow through points. It is important that candidates learn how to correctly input expressions into their calculators.

Although the question explicitly stated in bold to use the answer to part(b)(ii) many candidates used their answer to part (a) for part (c). The general notes about rounding in the mark scheme are over-ruled if the question has explicit directions such as in this question.