SOLUTION: if a:b is 3:5 and b:c is 4:7, what is a:b:c?

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Question 464833: if a:b is 3:5 and b:c is 4:7, what is a:b:c?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
if a:b is 3:5 and b:c is 4:7,
what is a:b:c?
:
a%2Fb = 3%2F5
Cross multiply
5a = 3b
a = 3%2F5b
and
b%2Fc = 4%2F7
cross multiply
4c = 7b
c = 7%2F4b
:
a:b:c
Replace a and c:
3%2F5b : b : 7%2F4b
Multiply by 20 to clear the denominators
4(3b) : 20b : 5(7)b
12b : 20b : 35b
therefore
a:b:c = 12:20:35