qiu zhi dao ~~~~

manmuma · 发表于 2013-9-14 23:59:28

A photographer will arrange 6people of 6 different heights for photograph by placing them in two rows ofthree so that each person in the first row is standing in front of someone inthe second row. The heights of thepeople within each row must increase from left to right, and each person in thesecond row must be taller than the person standing in front of him or her. How many such arrangements of the 6 peopleare possible?

A. 5

B. 6

C. 9

D. 24

E. 36

Please teach me how to solve it~~~~

cherriben · 发表于 2013-9-15 00:15:55

1 must be in first row

Enumerate first row
123
124
125
134
135

brentliang · 发表于 2013-9-15 00:21:45

consider 1 2 3 4 5 6 to be persons in increasing order fr heights…

so the arrnagements can be

456
123

246
135

346
125

256
134

356
124

A

manmuma · 发表于 2013-9-15 00:56:24

brentliang 发表于 2013-9-15 00:21
consider 1 2 3 4 5 6 to be persons in increasing order fr heights…

so the arrnagements can be

Thanks a lot~~

manmuma · 发表于 2013-9-15 00:57:42

cherriben 发表于 2013-9-15 00:15
1 must be in first row

Enumerate first row

duo xie la ~~~~

qiu zhi dao ~~~~

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