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View Full Version : Using Quadratic Equation, or Completing The Square


karebear11
Oct 12, 2008, 10:49 AM
A rectangular swimming pool measuring 10 m by 4 m is surrounded by a deck of uniform width. The combined area of the deck and the pool is 135 m^2. What is the width of the deck?


I have some idea of how to solve this problem. I'm guessing that by multiplying 10 m by 4 m, we have the area of the pool and subtract that (40 m^2) from the 135 m^2.

and then from there, it would be x^2 + 14x + 95?

galactus
Oct 12, 2008, 01:45 PM
You are on the right track, but have the wrong equation. But, you're are only off by a sign.

(4+x)(10+x)=135

Should be x^{2}+14x-95=0

x is the width of the walkway.

Credendovidis
Oct 12, 2008, 05:07 PM
x is the width of the walkway.
You're supposed to help with homework. Not do their homework !

:)

galactus
Oct 13, 2008, 05:18 AM
If you look, all I did was make a correction.

mluktuke
Oct 13, 2008, 12:20 PM
A woman starts with a certain number of quarters. She gives one fifth of the amount plus four more to her daughter. Then she gives one fourth of the remaining quarters plus three more to her son. Next she gives one third of what's left plus four more to her grandson, and finally one half of what remains plus five more to h granddaughter. After all of this, she is left with 10 quarters. How many did she start with? Who ended up with the most quarters?

Credendovidis
Oct 13, 2008, 04:33 PM
A woman starts out with a certain number of quarters.
Why don't you ask your own questions, instead of posting one here ?

To solve your problem : make the original amount of quarters "a".
Then start setting up the equations, and solve this easy problem yourself.

Example :

step 1 : 1/5 of a + 4 to daughter (=d) --> 1/5a+4=d
(remainder is 4/5a-4)

step 2 : 1/4 of rest + 3 to son (=s) --> 1/4 (4/5a-4)+3=s

etc. etc. etc.

After step four add everything together to get "a" again, and solve!

:)