During a sale, a clothing store sold each shirt at a price of $15 and each sweater at a price of $25. Did the store sell more sweaters than shirts during the sale?
(1) The average (arithmetic mean) of the prices of all of the shirts and sweaters that the store sold during the sale was $21.
(2) The total of the prices of all of the shirts and sweaters that the store sold during the sale was $420.
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.
shirt = x, sweater = y ,y>x?
(1) ,15x+25y=21x+21y,4y=7x,y>x。
(2) 15x+25y=420 不只一组解。
或者 直接想, 如果一边多的情况下平均数是20,现在是21,肯定卖25块钱的那个多。不用算具体数值,就是能回答多或者不多就可以了。
把化简之后的条件(1)带入条件(2)不可以算出来么
奥 知道了 犯糊涂了····
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算比值
第一个条件,总卖价的平均数是21,可以这么想,也就是shirt的销售数量多从而拉低了sweater25元的价格,所以可以推测出总的销售量中shirt所占比重大
(2) 15a+25b=420
因为件数只能是正整数,不能用一元二次方程有不止一个解来直接排除,用试数法。
15a+25b=420-->3a+5b=84, 84/5=16…4,b最大是16。5b=(0,5,10,15…75,80);用84分别减5b的极大极小值,看差数是否可以被3整除,得a的极大极小值为3,23,分别对应S>t,S
不用算出具体数量,看出比值就ok了