6. A cyclist rides at 5 metres per second. The wheels of his bicycle have a circumference of $125 \mathrm{~cm}$. How many complete turns does each wheel make in 5 seconds?
A 4
B 5
C 10
D 20
E 25
6. D In five seconds, the cyclist will have travelled $5 \times 5 \mathrm{~m}=25 \mathrm{~m}$. Hence the wheels will have made $25 \div 1.25=20$ complete turns.