Preston can paint 375 square feet in 3 hours. at the same rate, how long would it take him to paint 812.5 square feet?

0.15 hours
1.4 hours
7.5 hours
6.5 hours

6.5 hours

Step-by-step explanation:

First try to find the rate he can paint per hour

375 ÷ 3 = 125 ft^2 per hour

Then try to find how long it should take it for him to paint 812.5 sq ft

812.5 ÷ 125 = 6.5 hours

geometry: triangles

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lessons

answers archive

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