Aboat traveled in a river upstream for a distance of 30 miles at a constant rate, r, in miles per hour, and then made the return trip downstream at
a constant rate. if the boat took 4 hours to travel upstream and 3 hours to travel downstream, which system of equations could be used to find
the rate of the river current, c, in miles per hour?
answer
a) 3r - 3c=30
4r + 4c = 30
b)3r + 4c = 30
3r - 4c = 30
c)4r+ 3c = 30
4r - 3c=30
d) 3r+3c = 30
4r – 4c=30

D

Step-by-step explanation:

r = boat's rate

c = current's rate

1. A boat traveled in a river upstream for a distance of 30 miles. Travelling upstream, the current obstructs the movement, so the actual boat's rate is r - c mph.

If the boat took 4 hours to travel upstream, then

2. A boat traveled in a river downstream for a distance of 30 miles. Travelling downstream, the current helps the movement, so the actual boat's rate is r + c mph.

If the boat took 3 hours to travel downstream, then

So, we get the system

4r-4c=30

3r+3c=30

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

x= 149. 24+7=31. 180-31=149

your welcome