Question

A boat has a speed of 9 miles per hour in calm water. it takes the boat 4 hours to travel upstream but only 2 hours to travel the same distance downstream. which equation can be used to find c, the speed of the current in miles per hour? 2(9 â€” c) = 4(9 c) 9 c = 4(9 â€” c) 9 â€” c = 2(9 c) 4(9 â€” c) = 2(9 c)

1. Philomena
The equation which can be used to find c is (D) 4(9 – c) = 2(9 + c).

### What is an equation?

• An equation is a formula in mathematics that expresses the equality of two expressions by connecting them with the equals sign =.
• A mathematical statement made up of two expressions joined by an equal sign is known as an equation.
• 3x – 5 = 16 is an example of an equation.
• We get the value of the variable x as x = 7 after solving this equation.
To find the equation which can be used to find c:
• Since Distance = Speed × Time.
• Here c represents the speed of the current.
• Thus, if the boat has a speed of 9 mph in still water.
• Then its speed upstream = ( 9 – c ) mph.
• Also, It takes the boat 4 hours to travel upstream.
• Hence, total distance in upstream = 4 ( 9 – c ).
• Similarly its speed in downstream = ( 9 + c ) mph.
• Also, It takes the boat 2 hours to travel downstream.
• Hence, total distance in downstream = 2 ( 9 + c ).
• Since the distance upstream and downstream is equal.
• ⇒ 4 ( 9 – c ) = 2 ( 9 + c )
Therefore, the equation which can be used to find c is (D) 4(9-c)=2(9+c).