SOLUTION: A rectangular piece of tin 40cm by 30cm is to be made into an open box with a base of 900cm^2 by cutting equal squares from the four corners then folding up the sides. Find the len

Algebra ->  Coordinate Systems and Linear Equations  -> Linear Equations and Systems Word Problems -> SOLUTION: A rectangular piece of tin 40cm by 30cm is to be made into an open box with a base of 900cm^2 by cutting equal squares from the four corners then folding up the sides. Find the len      Log On


   

Question 831615: A rectangular piece of tin 40cm by 30cm is to be made into an open box with a base of 900cm^2 by cutting equal squares from the four corners then folding up the sides. Find the length of the sides of the square cut up from each side.
I drew it out and got the formula (40-2x)(30-2x) = 1200-4x^2 but am not sure how to solve or if I have the correct equation
Answer by josgarithmetic(39614) About Me  (Show Source):
You can put this solution on YOUR website!
Your equation is wrong, but you began with the correct expression for the left member.

Original area was 1200 cm^2. When the cuts and folds are done, length may become 40-2x, and width may become 30-2x, still acting as the base for the box. The base is given in this form, as 900 cm^2.

The symbolized situation for area of the base is: highlight_green%28%2840-2x%29%2830-2x%29=900%29;
NOW solve for x.

2%2820-x%29%2A2%2A%2815-x%29=9%2A2%2A2%2A5%2A5
%2820-x%29%2815-x%29=9%2A25
%2820-x%29%2815-x%29=225
300-15x-20x%2Bx%5E2=225
x%5E2-35x%2B300-225=0
highlight_green%28x%5E2-35x%2B75=0%29
Quadratic equation, general form. You can finish this.