1. square base area= 25 inches
2. using the slanted 6.5
=1/2base , therefore 5/2=2.5 inches
3. then use pythagoras.... c=6.5, a=2.5
c^2=a^2 + b^2
(do this urself)
4. when u find what b is... that's the height of one of the triangle
base= 2.5 (look at step 2 if u don't understand this bit)
height=b (refer to step 3)
5. then work out the area of 1 triangle using that...
6. then have (the answer u work out in step 5 ) multiply 4
this will give u the area for the all of the 4 triangles...
7. Then add together the square based area in step 1..(25)
to the 4 triangular, area faces (i.e from step 6) - the total will be ur answer for the amount of cardboard!!
p.s don't forget the units!!!