A department store is having a special sale on shirts. The price of the shirts is decreased by 10% each day of the sale. if the original price of a shirt in the department stire is $40, about how many days will it take for the price of the shirt to be less than $10?

the answer to this question is 3/19

step-by-step explanation:

geometry: triangles

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call the larger triangle abc

then the smaller triangle cde is similar to abc (all angles are equal, aaa).  

ab is the side that is 36, and we wish to find de, the side corresponding to ab

area_cde = area_abc - area_cde --> area_abc / area_cde = 2

let x=length of de

ratio of areas = (ratio of sides)^2

+2+=+%2836%2fx%29%5e2+

+2+=+1296%2fx%5e2+

++x%5e2+=+1296%2f2+=+648+

25.45584