There are 130 people in a sport centre. 76 people use the gym. 60 people use the swimming pool. 32 people use the track. 23 people use the gym and the pool. 8 people use the pool and the track. 20 people use the gym and the track. 6 people use all three facilities. Given that a randomly selected person uses at least two facilities, what is the probability they use all the facilities?

take it another

geometry: triangles

solvers

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

it should be a.

hope it