Expert: Richard J. Raridon - 3/24/2007

Question
QUESTION: Can you help with this one please

"A brick wall is seven times longer than its height.The builder then
decides to extend the wall,so he increases the height by 1m and the
length by 12m.The area of the wall has now been doubled.calculate the number
of bricks required to extend the wall if there are 120 bricks per
square metre
Please can you help with this i need to make a quadratic equation then
how to solve i need to practice this and is there any more good ones so
i can practice please help???"

ANSWER: L = 7H and (L+12)(H+1) = 2LH
so 7H^2 -19H -12 = 0 and H = 3.243 and L = 22.7
the new area is 147.24 m^2 which will take 17,669 bricks

---------- FOLLOW-UP ----------

QUESTION: please can you explain every step please so i can write this down and practice with others thankyou

Answer
Simple.  You have two equations, two unknowns.  Substitute
L=7H into the second equation to get (7H+12)(H+1) = 2(7H)H.
Multiply that out and rearrange it to get 7H^2-19H-12 = 0.
Solve using the quadratic formula. Once you have H and L, the new wall is 4.243 high and 34.7 long with an area of
147.24 m^2.  Multiply that by 120