Data:
1 litre = 1000 mL
If:
1000 mL → £3.50
200 mL → y
Solving: Rule of three (directly proportional)
\(\frac{1000}{200} = \frac{3.50}{y}\)
Product of extremes equals product of means:
\(1000*y = 3.50*200\)
\(1000y = 700\)
\(y = \frac{700}{1000}\)
\(y = 0.7\to \boxed{\boxed{y = \£0.70}}\end{array}}\qquad\quad\checkmark\)
