Question

1. The distance travelled downstream by a boat in 4 hours is 16km more than the
distance travelled upstream by the boat in the same time. What is the speed of
the current ? (in kmph)
1) 2
2) 3
3) 2.5
4) 3.5
5) 4​

Answer 1

The speed of the current is 2 km/h  .

Step-by-step explanation:

Given as :

The distance travel in upstream = d km

The time travelled = t = 4 hours

The distance travel in downstream = (d + 16) km

The time travelled = t = 4 hours

Let The speed of the boat = x km/h

Let The speed of the current = y km/h

According to question

∵   Distance = Speed × Time

For upstream

d = (x -y) × 4

For downstream

d + 16 = (x + y) × 4

From eq 1 and eq 2

(x -y ) × 4  + 16 = (x + y) × 4

Or, 4 x - 4 y + 16 = 4 x + 4 y

Or, ( 4 x + 4 y) - ( 4 x - 4 y ) = 16

or,  ( 4 x - 4 x ) + ( 4 x + 4 y ) = 16

or,  0 + 8 y = 16

∴              y = $\dfrac{16}{8}$

i.e            y = 2 km/h

So, The speed of the current = y = 2 km/h

Hence, The speed of the current is 2 km/h  . Answer