12. Kitu can row abwisulalltspeed of rowing in still water and the spe

1.	12. Kitu can row abwisulalltspeed of rowing in still water and the speed of the currerit.Lotor boat can travel 30 km upstream and 28 km downstreamin7 hours. It c[NCERT EXE21 km upstream and return in 5 hours. Find the speed of the boat inFleurs 30 mi
Answer» let the speed of the boat be x and the speed of stream be y 30/x-y + 28/x+y =7 21/x-y + 21/x+y=5 therefore 1/x-y=a,1/x+y=b 30a+28b=7...(1)×21 21a+21b=5.....(2)×30 630a+588b=147 630a+630b=150 (1)-(2/ -42b=-3 b=1/14 substituting the value of b in(1) a=1/6 a=1/x-y 1/6=1/x-y x-y=6...(.3) b=1/x+y 1/14=1/x+y x+y=14......(4) (3)+(4) 2x=20 x=10 x+y=14 y=14-10=4 therefore speed of boat in still water is 10km/hr and speed of stream is 4km/hr

12. Kitu can row abwisulalltspeed of rowing in still water and the speed of the currerit.Lotor boat can travel 30 km upstream and 28 km downstreamin7 hours. It c[NCERT EXE21 km upstream and return in 5 hours. Find the speed of the boat inFleurs 30 mi

Answer»

let the speed of the boat be x and the speed of stream be y

30/x-y + 28/x+y =7

21/x-y + 21/x+y=5

therefore 1/x-y=a,1/x+y=b

30a+28b=7...(1)×21

21a+21b=5.....(2)×30

630a+588b=147

630a+630b=150

(1)-(2/

-42b=-3

b=1/14

substituting the value of b in(1)

a=1/6

a=1/x-y

1/6=1/x-y

x-y=6...(.3)

b=1/x+y

1/14=1/x+y

x+y=14......(4)

(3)+(4)

2x=20

x=10

x+y=14

y=14-10=4

therefore speed of boat in still water is 10km/hr and speed of stream is 4km/hr