Question

Speed of the boat along the current and against the current are 10 km/h and 8 km/h respectively.
What is the speed of the current?

• A. 4
• B. 3
• C. 2
• D. 1

Answer 1

The Correct Option is D

The speed of the boat in still water is the average of its speeds along and against the current. Let \( b \) be the speed of the boat in still water and \( c \) be the speed of the current.
According to the given:
Speed along the current = \( b+c = 10 \) km/h
Speed against the current = \( b-c = 8 \) km/h
By adding these two equations, we have:
\( (b+c) + (b-c) = 10 + 8 \)
\( 2b = 18 \)
\( b = 9 \) km/h
Substituting the value of \( b \) in \( b+c=10 \):
\( 9+c=10 \)
\( c=10-9 \)
\( c=1 \) km/h