Euclid showed geometrically the distributed law of multiplication. Let bar(AB) and bar(BC)¯¯¯¯¯¯ABand¯¯¯¯¯¯BC be two straight lines, tracing a rectangle and let bar(BC)¯¯¯¯¯¯BCbe cut at random at the points D & E. Use this fact to show the distributed law?

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1 Answer
Sep 13, 2016

Please see below.

Explanation:

Let BD=pBD=p, DE=qDE=q and EC=rEC=r

then BC=p+q+rBC=p+q+r. Also let AB=aAB=a and hence AB=DH=EJ=aAB=DH=EJ=a.

Therefore area of rectangle ABCN=ABxxBC=axx(p+q+r)ABCN=AB×BC=a×(p+q+r) as BC=BD+DE+EC=p+q+rBC=BD+DE+EC=p+q+r

Also area of rectangles ABDHABDH, DEJHDEJH and ECNJECNJ are

ABDH=ABxxBD=axxpABDH=AB×BD=a×p

DEJH=DHxxDE=ABxxDE=axxqDEJH=DH×DE=AB×DE=a×q

ECNJ=EJxxEC=ABxxEC=axxrECNJ=EJ×EC=AB×EC=a×r

it is evident from the image that area of rectangle ABCNABCN is sum of areas of rectangles ABDHABDH, DEJHDEJH and ECNJECNJ.

Hence, axx(p+q+r)=axxp+axxq+axxra×(p+q+r)=a×p+a×q+a×r

which is nothing but the distributive law.