Answer:
[tex]V=90\ ft^3[/tex]
Step-by-step explanation:
-Given the two heights are similar:
#Heidi's flowered bed dimensions and volume is calculated as:
[tex]v=lwh[/tex]
[tex]=5\times 3\times 2\\\\=30\ ft^3[/tex]
#The width of Andrew's is twice Heidi's. The width and volume is thus calculated as:
[tex]w_a=2\times 3=6 \ ft\\\\V_a=lwh\\\\=5\times 6 \times 2\\\\=60\ ft^3[/tex]
#Total soil volume of the soil used is determined by summing the two different flowerbed volumes:
[tex]V=V_h+V_a\\\\=30+60\\\\=90 \ ft^3[/tex]