probability of building + probability of garden + probability of monument = 1
2/5 + 3/10 + x = 1
2(2) + 1(3) + 10(x) =10(1)
4 + 3 + 10x =10
10x = 3
x =3/10
Total cards (c) x probability of monument (3/10) = # of monument cards (9)
3/10c = 9
c = 9(10/3)
c = 30 Total postcards in the box
Total cards (30) x probability of building (2/5) = # of building cards (b)
30 x 2/5 = b
12 = b number of building postcards
Total cards (30) x probability of garden (3/10) = # of garden cards (g)
30 x 3/10 = g
9 = g number of garden postcards
Answers: 30 postcards, 12 building cards, 9 garden cards
4)
Total cards (c) x probability of building (2/5) = # of building cards (12 + 8)
c (2/5) = 20
c = 20(5/2)
c = 50
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Total cards (50) x probability of garden (3/10) = # of garden cards (g)
50 (3/10) = g
15 = g
There were 9 garden cards and now there are 15
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Total cards (50) x probability of monument (3/10) = # of monument (m)
50 (3/10) = m
15 = m
There were 9 monument cards and now there are 15 cards
Answer: 6 more garden and 6 more monument postcards
