Edexcel IGCSE Math A 4.11.A lengths in similar shapes

Scale examples:
$$\frac{15}{6},\quad \frac{6}{15},\quad \frac{4.2}{6},\quad \frac{6}{4.2}$$

Final answer:
10.5

Equivalent answers accepted.

$19.5 \div 2.5$ or $19.5 \times 0.4$ oe or
$4.2 \times \frac{19.5}{(\mathrm{a})}$

M1 If using DF ft their answer from part (a)

7.8

2

A1 oe

Total 4 marks

18

e.g. $30 \times 26.8(=804)$ or
$13 \times 25(=325)$ or
( 26.8-25 ) $\times 30$ or
$1.8 \times 30$

M1 for finding the total marks for the boys or the total test
marks

e.g. $(30 \times 26.8-13 \times 25) \div(30-13)$ (= 28.1764...) or ('804' - '325') ÷ (30 - 13) (= 28.1764...) or ('804' - '325' ÷ 17) (= 28.1764...) or $((26.8-25) \times 30) \div 17+25$ (= 28.1764...) or ${ }^{\prime} 1.8^{\prime} \times 30 \div 17+25(=28.1764 \ldots)$

M1 for a complete method to find the mean mark for the girls

28.2

3

A1 accept 28.15-28.2 (accept without working)
(Accept 28 from complete working)

Total 3 marks