6 月 JJ-242 请教

yuren1978

    

242.         liu同学兜里有21notes，1元，5元，10元，问各有几张？

    

(1). 一共90元。

    

(2). 一元的是10元的两倍

    

选D，都能算出来的

bth

Problem Stem:

# of 1 Dollar note = x

# ,,  5 ,,       ,,     = y

# ,,  10  ,,    ,,     = z

So, x+y+z =21.

 

Stem1:

X+5y+10z =90

X, y and z may be (10, 6, 5) (5, 15, 1). NOT SUFF.

 

Stem2:

X=2z. It does not help alone. NOT SUFF.

(x, y, z) = (14,0,7), (12,3,6), (10,6,5), (8,9,4), (6,12,3), (4 , 15,2), (2,18,1), (0,21,0)
            

From 1 and 2 we get that x, y and z are 10, 6, 5 respectively.

Answer is C.

billwang2008

kenzopeace的MATHJJ只整理到213题,拜托告知何处找到的242题,至谢!