GMAT
题目
Mark has twice as many oranges as George. Tony has 10 fewer than twice the sum of George and Mark’s oranges. If Tony were to give 15 oranges to George and 5 oranges to Mark, George and Mark would each have half the number of oranges Tony had originally. How many oranges did George have originally?
解析
首先，我们需要用乔治的橙子数量来表示托尼的橙子数量。
设 T = 托尼的橙子数， G = 乔治的橙子数，M = 马克的橙子数。
已知：
M = 2G
T = 2(G + M) - 10
将 \( M = 2G \) 代入上式：
T = 2(G + 2G) - 10
T = 2(3G) - 10
T = 6G - 10 [1]
此时我们可以完全忽略马克，因为我们只需要关注乔治的数量，这也是我一开始被卡住的地方。
“当托尼给乔治15个橙子后，乔治拥有的橙子数是托尼原本数量的一半”
这意味着：
G + 15 =T/2
即：
2G + 30 = T
将方程[1]中的 \( T \) 代入上式：
2G + 30 = 6G - 10
40 = 4G
10 = G
这就是我们的答案，选项A。
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