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Marta bought several pencils. If each pencil was either a 23-cent pencil or a 21-cent pencil, how many 23-cent pencils did Marta buy?
(1) Marta bought a total of 6 pencils.
(2) The total value of the pencils Marta bought was 130 cents.
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【答案】B
【思路】
(1) Out of the 6, any number of them can be 21 or 23……insufficient
(2) 2x+ 21(x+y) = 130
x+y =6
x=2, y=4……sufficient
ANS 是 B，但解答中出現了有 A的答案(X+Y=6)…… 正確是Ｃ？？？
我自已原本算也是 C，但正確是 B
怪怪滴
