Answer :

theorem1:- The Rule of Three is a Mathematical Rule that allows you to solve problems based on proportions. By having three numbers: a, b, c,

(a)Direct proportions rule of 3:-

if ab

c then

(b)inverse proportions rule of 3:-

if ab

c then

formula:- (i)direct method----

(ii)indirect or inverse proportions xy=k

given:-

method used is called direct method

for 1 pen is 112.5/25= 4.5cost

so,12 pen cost is 4.5x12=54

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