Answer:
19.0km/h (rounded to 3 s.f.)
Step-by-step explanation:
To find the speed, we need to find the distance travelled per second before finding the distance per hour (speed).
1 revolution = [tex]\pi[/tex] × 84
= 84[tex]\pi[/tex] cm
= 0.00084[tex]\pi[/tex] km
2 revolutions = 0.00084[tex]\pi[/tex] km × 2
= 0.00168[tex]\pi[/tex] km
1 second --- 0.00168[tex]\pi[/tex] km
1 minute --- 0.00168[tex]\pi[/tex] km × 60 = 0.1008[tex]\pi[/tex] km
1 hour --- 0.1008[tex]\pi[/tex] km × 60 = 6.048[tex]\pi[/tex] km
= 19.0 km (rounded to 3 s.f.)
