Traveling upstream (against the current) in a boat, you can travel 35 miles in 7 hours. It takes half the time (3.5 hours) to travel the same distance downstream (with the
current). Find the speed of the current.

The speed of the current is 2.5 miles per hour

Step-by-step explanation:

Systems of Equations

Let's call:

B = velocity of the boat

C = velocity of the current

When traveling upstream, the current is against the boat thus the relative velocity is B-C.

The distance is the product of the velocity by the time. Since the boat takes 7 hours to travel 35 miles upstream, thus:

d=(B-C)*7=35

Dividing by 7:

B - C = 5       [1]

When traveling downstream, the current and the boat are collaborative and the relative velocity is B+C. The travel takes now 3.5 hours, thus:

d=(B+C)*3.5=35

Dividing by 3.5:

B + C = 10       [2]

Subtracting [2] - [1]:

2C = 5

C = 5/2 = 2.5

The speed of the current is 2.5 miles per hour

answer: the area of the parallelogram below is 42 square meters.

- officialprodixy ☕