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The stiffness of a beam of rectangular cross section is proportional to the breadth and the cube of of the depth. If the breadth is 20 cm., express the stiffness as a function of the depth.

Sagot :

Rider21viz
let s = stiffness
     b = breadth
     d = depth

s = bd^3

just substitute the given value for breadth:

s = 20d^3   ans...