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Question

Mark rows a boat 8 miles an hour in calm water. When the rate of a river’s current is 3 mph, it takes Mark 2 hours longer to row a given distance upstream than to travel the same distance downstream. How long will it take him to row downstream? How many miles will he row in total?

Answer 1

distance = rate of speed times time

d =rt

D= time downstream D+2 = time upstream

(8+3)(U) = (8-3)(U+2

11D = 5D +10

6D = 10

D = 10/6 = 5/3 = 1 2/3 hours = 100 minutes for time downstream

D+2 = 2+5/3 = 3 2/3 hours upstream

11 x 5/3 = 55/3 = 18 1/3 miles = total distance one way

36 2/3 miles = total distance up and down stream

Answer 2

Rate upstream = 5

Rate downstream = 11

T=time downstream

T+2=time upstream

11T = 5(T+2)

6T=10

T=5/3 (i.e. 1 hr and 20 minutes)

You figure the answers from here.

Answer 3

d = r * t

d = (8 - 3)(t + 2)

d = (8 + 3)(t)

Can you solve for do or t and answer?