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题库 / GMATLA-DS-46
What is the ratio of the average (arithmetic mean) height of students in class X to the average height of students in class Y?
(1) The average height of the students in class X is 120 centimeters.
(2) The average height of the students in class X and class Y combined is 126 centimeters.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
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设平均数为x，y，人数为a，b。求x/y
(1)x=120
(2) (ax+by)/(a+b)=126-->120a+by=126a+126b,三元一次方程除非接触x等于y的倍数，不带尾数，才能得出x/y，四元一次方程更难。
(1)(2)联立，得出y=6(a/b)+126，不知道a/b，无法求出x/y的值。
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