恳请各位帮帮忙~~~~OG12 87

pangpangshin

87. A necklace is made by stringing N individual beads
together in the repeating pattern red bead, green
bead, white bead, blue bead, and yellow bead. If the
necklace design begins with a red bead and ends with
a white bead, then N could equal
(A) 16
(B) 32
(C) 4 1
(D) 54
(E) 68

答案是E,这是OG的解释：

Algebra Applied problems
Th e bead pattern repeats after every fifth bead.
Since the first bead in this design (or the first in
the pattern) is red and the last bead in this design
(or third in the pattern) is white, the number of
beads in this design is 3 more than some multiple
of 5. Th is can be expressed as 5n + 3, where n is
an integer. Test each of the answer choices to
determine which is a multiple of 5 plus a value
of 3. Of the options, only 68 = 5(13) + 3 can be
written in the form 5n + 3.

问题：
1、(or third in the pattern) is white  白色不是排最后嘛？怎么又变成第三了?
2、the number of
beads in this design is 3 more than some multiple
of 5.   这话咋理解呢~~~~~~
3、5n + 3 这又是咋回事呢~~~~~~~


谢谢·~~~各位~~~~~麻烦帮帮忙~~~~

JoshwuS

1）红绿白蓝黄循环排列，题目说第一颗珠子是红色，按1到5编号，白色编号3
2）这个以转化为一个商数为5，余数为3的数学问题
3）同上

pangpangshin

1、不是说白色是排最后嘛？那编号不是应该是5吗？
2、3 还是不懂为什么会这样列式~~~能否再讲得清楚点呢？

哎。。。。看来还是我太笨了

natalietong

红绿白蓝黄排序是固定不变的，白色排最后意思是排到白的就没了，比如说

红绿白蓝黄／红绿白蓝黄／红绿白，所以这是一个余数为3的问题。

不知道这么解释清楚不??

pangpangshin

天啊！！！！！！！太精辟了！！！！！！！谢谢！！！