David can finish painting the room in six hours and his elder brother Anthony can finish it in four hours if both brothers paint the room together how many hours will it take them and how many minutes

2.4 hours

Step-by-step explanation:

David's time = 6 hours

Anthony's time = 4 hours

the combined time is given by the following formula

1/ (david's time) + 1/(anthony's time) = 1/total time

1/6 + 1/4 = 1/Total

4/24 + 6/24 = 1/Total

10/24 = 1/ total   (taking reciprocal of both sides)

24/10 = total

total time = 24/10 = 2.4 hours

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

144.50

step-by-step explanation:

21.5 x 13.4=288.10 divide by 2