A launch approaching a cliff at reduced speed sounds a short blast and the echo is heard after 10 seconds. Five minutes after sounding the first blast she again sounds a blast and the echo is heard after 8 seconds. What is the speed of the launch? The velocity of sound is 330 ms (raised to) -1.

1.1m/sThe sound while echoing travels double distance .the echo was heard at 10s which implies that it takes 5s to reach the cliff from 1st point. Speed of sound is 330m/s. That implies distance traveled by it is 330×5=1650 m.Similarly the distance travelled from 2nd point comes 1320m.It means that the distance travelled by the launch in 5min (5×60=300sec) is (1650-1320)=330m. That implies speed is 330/300=1.1m/s