sat数学题 twice as many A as

题目

sat数学题 twice as many A as
During a visit by the census taker,one child in a
family said,“I have twice as many brothers as sisters.”
Another child in the family said,“I don’t.I have the
same number of brothers and sisters.” How many
children are there in the family?
题目中有一句 “I have twice as many brothers as sisters.”我上网查了一下twice as many A as 之前的前辈都说 B是A的两倍.但是这道题最后的答案是 4 boys 和 3 girls,总共7个小孩,这样子的话,那句的意思就是brothers是sisters的两倍咯?
纠结了很久

答案

应该是A是B的两倍,所以
第一个小孩是女孩,所以她看家里就是 4个男孩,2个女孩,所以brothers是sisters的两倍
第二个小孩是男孩,所以他看家里就是 3个男孩,3个女孩,所以,brothers 和sisters 一样多
看到类似的题,先逻辑分析一下,可以判断出第一个小孩是女孩,第二个小孩是男孩,接下来就容易了
假设男孩总数是X,女孩总数是Y
第一个女孩看到的是：x=2(y-1)
第二个男孩看到的是：(x-1)=y
然后解一下,x=4,y=3 这样就大功告成了!
SAT数学没有什么难题,对于中国人来说,读清楚题目,理解题目意思很重要.无论题目难易,都要仔细读题,不然会中招 :P