Algebraic question

Question

A cereal packet is a cuboid with height 12 cm. The depth of the box is 4 cm more than the width, and the volume is 480 cm^3. Find the width of the box.

Answer 1

about 4.6 cm wide

8.6 cm deep

12(4.6)(8.6= about 480 cm^3

480=hdw = h(w+4)w =12(w^2+4w) = 12w^2 +48w

w^2 +4w - 40 = 0

w = -4/2 + (1/2)sqr(16 +160) = about 4.633 cm

d=about 8.633 cm

hdw = about (12)(8.633)(4.633) = about 479.9 cm^3