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John has US and foreign stamps in his album. The ratio of the number of US stamps to foreign stamps is 5 : 2. After Paul gives him 12 foreign stamps, the ratio becomes 2 : 1. Find the number of US stamps he has.

 Jun 6, 2021

Best Answer 

 #1
avatar+208 
+1

d=number of domestic stamps

f=number of foreign stamps 

\(\:\frac{d}{f}=\frac{5}{2}\)

\(2d=5f\)

\(\frac{d}{f+12}=\frac{2}{1}\)

\(d=2f+24\)

substitute d in first equation: 

\(2(2f+24)=5f\)

\(f=48\)

\(d=120\)

 

 

 

 

 

JP

 Jun 6, 2021
 #1
avatar+208 
+1
Best Answer

d=number of domestic stamps

f=number of foreign stamps 

\(\:\frac{d}{f}=\frac{5}{2}\)

\(2d=5f\)

\(\frac{d}{f+12}=\frac{2}{1}\)

\(d=2f+24\)

substitute d in first equation: 

\(2(2f+24)=5f\)

\(f=48\)

\(d=120\)

 

 

 

 

 

JP

JKP1234567890 Jun 6, 2021

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