Assertion: speed | /r/HasProperty | about 343 metres per second
Facets:
value: at 20 °c
type: TEMPORAL
Source sentences:
text: At 20 °C (68 °F), the speed of sound in air is about 343 metres per second (1,235 km/h; 1,125 ft/s; 767 mph; 667 kn), or a kilometre in 2.9 s or a mile in 4.7 s.