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The Philatelist Problem

My sister has six red stamps and three blue ones. In her collection, seven stamps are from Mexico and six stamps are from France. One stamp is purple and it is not from Mexico or France. Two of her Mexican stamps are red and one is blue. Two of her French stamps are blue and three are red. How many stamps does she have?

Answer:

She has a minimum of 15 stamps.
Mexico: 1 blue, 2 red, 4 unknown color
France: 2 blue, 3 red, 1 unknown color
Unknown country: 1 purple, 1 red

Stamps from Mexico
Seven stamps from Mexico (2 red, 1 blue)

Stamps from France
Six stamps from France (3 red, 2 blue)
Postage stamps
Two other stamps (1 red, 1 purple)
Total red stamps: six. Total blue stamps: three.

... and for all we know, she might also have 2 green stamps from Germany.*

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* Thanks to Keith Austin for pointing this out.

© Copyright  - Antonio Zamora

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