GEE asked in Science & MathematicsMathematics · 9 years ago

# Math Word Problem ..........?

A boat is went 10km downstream in 2 hours. on the way back it took 4 hours to go 8km against the current. determine the boats average speed and the speed of the current

please show all steps thank you

Relevance
• 9 years ago

speed x time = distance

If we call the speed of the boat r and the speed of the current c then the speed going

downstread is (r + c) and we have

(r + c) 2 = 10

Going upstream the current reduces the total speed and you have

(r - c)4 = 8

expanding these out we have

2r + 2c = 10 and

4r - 4c = 8 we can divide this 2nd equation by 2 on both sides to get

2r - 2c = 4 and we solve by ellimination by adding the first equation to this

2r + 2c = 10

----------------

4r = 14

so r = 14/4 = 7/2

Knowing that we can get c. Plug r = 7/2 into

2r + 2c = 10 to get

7 + 2c = 10 then

2c = 10 - 7 = 3 then

c = 3/2

• Anonymous
9 years ago

10/2 = 5km/hr

8/4 = 2km/hr

4 hours is 66% of the time, 2 hours is 33% of the time, so .33 * 5 + .66 * 2 = 2.89 km/hr is the average speed.

Speed of the current:

5-2 = 3 km/hr

• Anonymous
9 years ago

Is the speed of the current not 1.5..

let x be the speed of the boat unchanged

5km/h-xkm/h=2km/h+xkm/h

3=2x

x=1.5km/h

• 4 years ago

If something is 40% smaller, you merely subtract 40%. So 40% of 40 energy is sixteen: you are attempting this by utilising multiplying 40 by utilising 0.4. the respond could be 40 - sixteen = 24 A shorter way could merely be to multiply by utilising 40 by utilising 0.6, because's a million-0.4.