Posted by **nicole** on Friday, September 13, 2013 at 7:43pm.

by cutting a square out of each corner of a sheet of card (30cm by 21cm)and folding up the sides,i ca make an open box with a capacity of 1080cm^3.What is the area in cm^2 of each of the squares i have to cut out?

- math -
**Steve**, Friday, September 13, 2013 at 7:46pm
this problem has been solved in many of the related questions below, with different numbers. Follow some of them and give it a shot. What do you get?

- math -
**Graham**, Friday, September 13, 2013 at 8:16pm
Let the sides you cut out be x centimetres long.

The volume is then:

(30-2x)(21-2x)x = 1080

Expanding:

4 x^3 - 102 x^2 + 630 x - 1080 = 0

Look for common factors:

(x-3)(4x^2 - 90x + 360) = 0

Found one root, solve the quadratic for the other.

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