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Re: If John has exactly 10 coins each of which was minted in 1910 or 1920
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23 May 2020, 06:26
John has exactly 10 coins each of which was minted in 1910 or 1920 or 1930, how many of his coins were minted in 1920 ?
Statement (1) Exactly 6 of his coins were minted in 1910 or 1920.
But how many in 1920?
All 6, 5,4,3... Or nothing. (Insufficient)
Statement (2) Exactly 7 of his coins were minted in 1920 or 1930.
But how many in 1920?
All 7,6,5,.... Or nothing at all.
(Not sufficient)
1&2: let 1910 be A
1920 be B and 1930 be C
A+B=6 ------(1)
B+C=7 ------(2)
A+B+C=10 ----(3)
Equate 1&3
C=4
And from equation 2&3
A=3
Therefore B=3
So 3 coins were minted in 1920
Answer is C
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