Mach 0.82 equates to about 624.2 mph
The speed of sound varies depending on many factors. It is roughly 768 mph in dry air. Mach 1 is this speed under same conditions. So, .785 Mach would be 768 times 0.785, or 78.5% of 768 miles and hour. Roughly 603 mph at ground level in dry air and STP.
The speed of sound is different at various altitudes.
At sea level altitude, i.e. right beside any beach, Mach 0.7 is 563 mph.
At an altitude of 35,000 ft, which is a typical cruise altitude of a Boeing 747, Mach 0.7 is equivalent to 463 mph.
Just subsonic in air.
Perhaps at 630 mph.
Mach = Velocity/Velocity of sound in medium
Mach 0.885 = about 656.3 mph
Mach 0.77 is 586.13 mph
Mach 0.81 = 992.3 km/h
7.65 MPH= Mach 0.01
Mach 0.72 is about 552.4 mph
Mach 889 is about 659,233 mph
Mach 6 is about 4,449.3 mph
1,750.8 mph
Mach 1 is about 762 mph, so mach 20 is about 15,240mph.
About 761 mph
Mach 1.7 is equal to about 1294 mph.
645.38104_MPH_">645.38104 MPH-is 0.87 Mach -
about 655 MPH
3044.83 mph
1534.54 mph
about 5100 mph
4567.24 mph