after this banta takes t2 time to get to the end and santa takes (t2- 12/60)= (t2- 1/5)

total distance is 12 so we have two equation 

6t1 + 3(t2-1/5) = 12                         { 3 becuase after time t1 santa rows at half of the initial speed}

for banta 

4t1+ 4t2= 12

solving these two we get t1 = 1.2 

so before he lost his paddle he rowed = 6*1.2= 7.2 

distance from the end of the race =12-7.2 =4.8

Two kayak racing champions Santa and Banta challenge each other to a 12 km downstream kayak race. Santa rows downstream at 6kmph whereas Banta rows the same stretch at 4 kmph. They start at the same time from the same place but at one point, Santa loses his paddle and if forced to complete the remaining part of his race at half the initial speed. If he loses the race by 12 mins, how many kms from the end did he lose the paddle?

3

4

4.8

Hi Nikita, the water will apply force perpendicularly so instead of swimming 100 m he will swim 125 m in 5 min so given right angled traingle will be formed and water will cover 75 m in the same time.