数学题:养猪大户王师傅说他的猪卖75头，剩下的饲料可以喂20天，卖100头剩下的饲料可以喂25天，问王师傅总共喂了多少头猪?

数学题解答：这道题要求的是猪的总数，题中每头猪每天吃的饲料应该是按一定的量来计算的。两种所描述的两种情况中，剩下的饲料应该是相同的，可以利用这一点找到等量关系式。还有饲料的数量用猪的头数与天数的乘积来表示。

用方程解答如下：设总共喂了x头猪。

(x – 75)×20 = (x – 100)× 25

展开后，得：20x – 1500 = 25x – 2500

方程两边同时减去20x，再同时加上1500，得：

5x – 1000 = 0

x=200

答：养猪大户王师傅总共养了200头猪。

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