Question

a boat goes 30 km and 44km down stream in 10hours .In 13hours it can go 40 km up stream and 55km down stream. determine the speed of the stream and that of the both in still water

Answer 1

Its NCERT example 19 on page no. 65 u can see there

Answer 2

Answer:

Time= dis/speed

Case 1

Speed    distance       Time

x-y             30                30/x-y   ......1

x+y              44              44/x+y    ..........2

From 1& 2

30/x-y +44/x+y =10 ........3

Case2

Speed     Distance    Time

x-y               40            40/x-y   .........4

x+y              55             55/x+y   ..........5

From 4 & 5

40/x-y + 55/x+y =13  .........6

Since 1/x-y = v

         1/x+y = u

3..... 30v+44u = 10

6...... 40v+55u= 13

3..x4 ... 120v + 176u = 40

6...x3.... 120v +165u = 39

Use elimination method

Step-by-step explanation: