Question

Julie and Eric row their boat (at a constant speed) 55 miles downstream for 5 hours, helped by the

Answer 1

Answer: C = 3 mph is the rate of the current.

Step-by-step explanation:

Hey there!

You can use the distance formula (d = rt) to solve this problem.  

Downstream trip: d = 55 miles, t = 5 hours, and r = R + C  

R + C is their rowing speed (R) plus the rate of the current (C).  

Upstream trip: d = 55 miles, t = 11 hours, and r = R - C

R - C is their rowing speed (R) minus the rate of the current (C).  

Downstream: 55 mi. = (R + C)5 hrs. Divide both sides by 5: R + C = 11

Upstream: 55 mi. = (R - C)11 hrs. Divide both sides by 11: R - C = 5

Calculations

R + C = 11 Subtract C from both sides.

R = 11 - C Substitute this into: R - C = 5

(11 - C) - C = 5 Simplify and solve for C

11 - 2C = 5 Add 2C to both sides.

11 = 2C + 5 Subtract 5 from both sides.

6 = 2C Divide both sides by 2

C = 3 mph is the rate of the current.

~I hope I helped you! :)~