Home
Class 8
MATHS
The speed of a sub marine over sea surfa...

The speed of a sub marine over sea surface is 30 knot per hour and below sea surface is 20 knots per hour. What is the average speed of the submarine if it is below water surface for 3/4th of her time of journey What is the average speed of the submarine if it is under water surface for 3/4th of the total distance covered by him.

Text Solution

Verified by Experts

1)`V_(avg)`=(total distance/total distance)
`=(30*T/4+20*3T/4)/T=45/2`
2)Total distance=d
`T_1=(3/4d)/20`
`T_2=(1/4d)/30`
`V_(avg)`=Total distance/total time
`=D/((3/4D)/20+(1/4d)/30)`
`=240/11` .
Promotional Banner

Similar Questions

Explore conceptually related problems

A car covers a distance of 276.75 km in 4.5 hours. What is the average speed of the car ?

A train took 4 hours and 30 minutes to cover 360 kilometres. What is its average speed?

A car covers a certain distance in 3 hours at the speed of 124 kms/hr . What is the average speed of a truck which travels a distance of 120 kms less than the car in the same time ?

A boy travels a distance of 8 km at the rate of 4 km per hour , 6 km at the rate of 3 km per hour and 4 km at the rate of 2 km per hour. What is the average speed for the entire journey ?

A boat covers a distance of 14 km in 4 hours along the flow. What is the speed of the boat in still water, if the speed of the flow of water is 2 km/h?

Juan bikes halfway to school at 9 miles per hour, and walks the rest of the distance at 3 miles per hour. What is Juan's average speed for the whole trip?