A wheel of a cart makes 2 revolutions per second. If the diameter is 84 cm, find the speed in km/h

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 = × 84

                   = 84 cm

                   = 0.00084 km

2 revolutions = 0.00084 km × 2

                      = 0.00168 km

1 second --- 0.00168 km

1 minute --- 0.00168 km × 60 = 0.1008 km

1 hour --- 0.1008 km × 60 = 6.048 km

                                            = 19.0 km (rounded to 3 s.f.)

based on context clues you gave i'm assuming the answer would be c.