Question

A river is flowing with a steady speed of 4 km/h. One rows his boat downstream in the river and then returns by rowing upstream in the same river. When he returns to the starting point, the total distance covered by him is 42 km. If the return journey takes 2 h more than his outward journey, then the speed of his rowing in still water must be
A). 12 km/h
B). 10 km/h
C). 9 km/h
D). 8 km/h​

Answer 1

Step-by-step explanation:

According to the question, 21u+4+2=21u−4

=> 21+2u+8u+4=21u−4

=> 2u+29u+4=21u−4

=> (u−4)(2u+29)=21(u+4)

=> −8u+29u−116=21u+84

=> +21u−116=21u+84

=> 2u^{2}2u

2

=84+116=>

$2u^{2}$

=200

=> =100

=> u = 10 km/h