A fish and chips truck sells three kinds of fish: cod, haddock, and halibut. During a music festival, the truck sold 220 pieces of fish, of which $40 \%$ were haddock and $40 \%$ were halibut. How many pieces of cod did the truck sell?
The cod accounts for $100 \%-40 \%-40 \%=20 \%$ of the total pieces of fish sold.

Therefore, the number of pieces of cod sold was $0.2 \times 220=44$.

ANSWER: 44