a:b=2:3
b:c=4:5
then a:c=
a : b = 2 : 3 and b : c = 4 : 5
Therefore : a / b = 2 / 3 and b / c = 4 /5
Now Cross multiply each :
3a = 2b and 5b = 4c
Now : b = (3/2)*a and b = (4/5)*c
Comparing both : (3/2)*a = (4/5)*c
a / c = (4/5)*(2/3)
a / c = 8 / 15
Therefore : a : c = 8 : 15
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