Toh Xia Ping's answer to Rosie's Secondary 3 A Maths Singapore question.

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Toh Xia Ping
Toh Xia Ping's answer
20 answers (A Helpful Person)
1st
Carbon monoxide is formed due to the lack of oxygen which results in petrol undergoing incomplete combustion.

Improved system has more air circulating which suggest increase in amount of oxygen. Therefore, this decreases the rate of incomplete combustion occurring, lowering amount of carbon monoxide produced.