Two thirds of an hour =40 minutes =2400 seconds.

4/9 hours = 1600 seconds

600000÷2400=250

M/s < 3× 10？ Every second = 300m/s.

600000÷ 1600=375

M/s > 3× 10？ Every second = 300m/s.

So the second plane is supersonic.

2、2^a=3

2^b=6

2^c= 12

2^b=6=3×2=2^a×2=2^(a

1)

∴b=a

1

b-a= 1>0

B > a。

2^c= 12=6×2=2^b×2=2^(b

1)

∴c=b

1

c-b= 1>0

That's c > b

∴c>b>a

Similarly:

a