In a country where the labour force is 20 million, 17 million people are employed, and 1 million people have given up looking for work, what is the official unemployment rate?

The official unemployment rate uses the labour force as the denominator. The number unemployed is $20\text{ million} - 17\text{ million} = 3\text{ million}$. The unemployment rate is therefore $\frac{3}{20} \times 100 = 15\%$. The 1 million discouraged workers are already excluded from the labour force figure given, so no further adjustment is needed. Option C (5%) incorrectly excludes discouraged workers from the unemployed count.