Volume of one pyramid = 408.6*(755.9*755.9)*1/3
volume of 3 pyramids= 3*408.6*(755.9*755.9)=700,403,500.11*1/3=233,467,833.37
reasoning 3 square base pyramid = 1 cuboid
I believe they saved 48.32 together because $36.24 divided by 3 is $12.08 and $36.24 + $12.08 = $48.32
quadratic equations can be soled by 3 methods
factorization
completing square
quadratic formula
but factorization is the simplest
Yes 1,120 gallons per week (7 days)
Just divide 800 by 5 and see that the sprinkler system uses 160 gallons a day. Multiply 160 by 7 for the amount used a week and you will find that the answer is 1,120 gallons of water.
Let the amount invested at 4% be = x
Let the amount invested at 3% be = y
Given is:
or 
.... (1)
As, total income for the two investments is $194, so equation is:
....(2)
Putting value of x from (1) in (2)
And x=5200-y
Hence, money invested at 4% is $3800 and money invested at 3% is $1400
