# math

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A boat traveled 45 miles downstream (w/ the current) in 3 hours and made the return trop (against the current) in 5 hours. What was the speed of the boat and what was the speed of the current?

• math -

b=boat (mph)
c=current (mph)

Set up equations using distance=speed*time
3(b+c)=45 ...(1)
5(b-c)=45 ...(2)

Multiply (1) by 5 and (2) by 3:
15b+15c = 225 ...(1a)
15b-15c = 135 ...(2a)

Add (1a) and (2a)
30b+0 = 360
b = 360/30 = 12

Subtract (2a) from (1a)
0+30c = 90
c = 90/30 = 3

Boat speed is 12 mph,
current speed is 3 mph

• math -

speed of boat ---- x mph
speed of current -- y mph

then :
1. 3(x+y) = 45 or x+y = 15
2. 5(x-y) = 45 or x-y = 9

2x = 24
x = 12

from one of the others, y = 3

etc.

• math -

thank you guys so much

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