sanchi can row her boat at …

Let the speed of the stream be x km/hr Speed of the boat upstream=(5−x)km/hr Speed of the boat downstream=(5+x) km/hr Time taken for going 5.25km upstream = 5−x 5.25 ​ hours Time taken for going 5.25km downstream = 5+x 5.25 ​ hours Obviously, time taken for going 5.25km upstream is more than the time taken for going 5.25km, downstream It is given that the time taken for going 5.25km, upstream is 1 hour more than the time taken for going 5.25 downstream ∴ 5−x 5.25 ​ − 5+x 5.25 ​ =1 ⇒5.25{ 5−x 1 ​ − 5+x 1 ​ }=1⇒ 4 21 ​ ( (5−x)(5+x) 5+x−5+x ​ )=1 ⇒ 4 21 ​ × 25−x 2 2x ​ =1⇒ 2 21 ​ × 25−x 2 x ​ =1 ⇒2x 2 +21x−50=0 ⇒x(2x+25)−2(2x+25)=0⇒(2x+25)(x−2)=0 ⇒x−2=0,2x+25=0 ⇒x=2[∵x  = 2 −25 ​ ] ∴ speed of the stream =2km/hr