Question

a man starts from P and reaches Q in 9 hours after travelling half the distance at 5 km/h and remaining at 4 km/h .find the distance between P and Q.​

Answer 1

Answer:

Distance between P and Q is 40km

Step-by-step explanation:

Let d be the distance between P and Q

For first part of the journey

Speed = 5 km per hour

Time = t (say)

Distance = d/2

Now, Distance  = Speed x Time

=> d/2 = 5*t ............Eqn 1

For second part of the journey

Speed = 4 km per hour

Time = (9 - t) ..........total time = 9 hours and time for first part = t

Distance = d/2

Now, Distance  = Speed x Time

=> d/2 = 4*(9 - t) ..........Eqn 2

Equating Eqn 1 and Eqn 2,

5*t = 4*(9 - t)

5t = 36 - 4t

9t = 36

t = 4

Substituting for t in Eqn 1, we get:

d/2 = 5*4

d/2 = 20

d = 40

The distance is 40 km

Check:

Half distance = 20 km at 5 km per hour will take 4 hours

Half distance = 20 km at 4 km per hour will take 5 hours

Total time taken = 9 hours, as given.

Answer 2

Answer:

40

Step-by-step explanation:

first do 5x4 km/hr

=20x2=40 km/hr