rational equations ( i need help )

[vcanezal]

5. the water current is 3mph. going upstream for 36 miles against the current takes one hour longer than going the same distance downstream with the current. find the speed of the boat in still water. thanks?

7. together bart and lisa require 3 hours and 36 mins to clean the house. Alone, bart would require 3 hours more than lisa. how long would it take lisa to clean the house alone? pls incluce the equation and how to solve it

thanks

[stapel_eliz]

5. the water current is 3mph. going upstream for 36 miles against the current takes one hour longer than going the same distance downstream with the current. find the speed of the boat in still water. thanks?

To learn how to set up and solve "uniform rate" problems, try here.

If the boat's rate (according to the speedometer) is "b", then upstream is b - 3 and downstream is b + 3. Use "d = rt", etc.

7. together bart and lisa require 3 hours and 36 mins to clean the house. Alone, bart would require 3 hours more than lisa. how long would it take lisa to clean the house alone? pls incluce the equation and how to solve it

To learn how to set up and solve "work" problems, try here.

It would probably help to convert the times to just hours (15/5 and 3) or just minutes (216 and 180), in order to simplify calculations.

There are loads of worked examples, tables, and explanations. Once you've studied the lessons, please attempt the exercises. If you get stuck, please reply showing your efforts so far. Thank you!

[vcanezal]

5. i got 15 in still water by this equation.[36/x-3 minus 36/x+3 = 1] LCD=(x-3)(x+)
36x+108-36x+108=x^2-9
216=x^2-9
216+9=x^2
square root of 225 +or- =square root of x^2
15=x since its still water. idk if i did it right tho

7. idk. got stuck with the decimals. [(1/x+3)(3.36) + (1/x)(3.36)= 1] xLCD( x+3)(x) to get rid of fractions
[3.36x+(x+3)3.36=(x+3)(x)
3.36x+3.36x+10.08=x^2+3x
-3x+6.72x+10.08=x^2
3.72x+10.08=x^2 and im stuck. save me

[little_dragon]

15=x since its still water. idk if i did it right tho

check by sticking it back in:
down: 15+3=18, 36/18=2hrs
up: 15-3=12, 12*3hr=36
so it checks & its rite

7. idk. got stuck with the decimals. [(1/x+3)(3.36) + (1/x)(3.36)= 1] xLCD( x+3)(x)

"3.36" isn't 3hr 36min
use the fractions they gave u before