Question

A boat goes down stream in 9 hours.it cover the same distance up stream in 10 hours .if the speed of the stream is 1km/h,then find the speed of the boat​

Answer 1

Let :

• Distance traveled= x km
• Speed of boat = v km/h

.

Given :

• Time taken to cover distance 'x' down stream= 9 hours
• Time taken to cover distance'x' upstream = 10hours
• Speed of stream = 1 km/h

To find :

Speed of boat (v)

Formula used :

Distance = speed × time

Solution :

✪ When boat move downstream

◈ Distance = x km

◈ Time = 9 hours

◈ Net speed of boat downstream = Speed of boat + speed of stream

➠ Net speed of boat downstream = v km/h + 1 km/h

◈ Using , Distance = speed × time

➠ x = (v+1) km/h × 9 h

➠ x = 9(v+1) km ...... equation 1

✪ When boat move upstream

◈ Distance = x km

◈ Time = 10 hours

◈ Net speed of boat upstream = Speed of boat - speed of stream

➠ Net speed of boat downstream = v km/h - 1 km/h

◈ Using , Distance = speed × time

➠ x = (v-1) km/h × 10 h

➠ x = 10(v-1) km ...... equation 2

◈ Comparing , equation 1 & equation 2

we get;

➠ 9(v+1) = 10(v-1)

➠ 9v + 9 = 10v - 10

➠ 10v - 9v = 9 + 10

➠ v = 19

ANSWER :

Speed of boat (v) = 19 km/h