Bunuel
In how many ways can 3 identical blue roses and 3 identical red roses be arranged in a circle?
A. 2
B. 3
C. 4
D. 5
E. 8
We can have three cases -
Case 1: No roses of the same kind are togetherAs no two roses of the same kind can be placed together, the roses have to be arranged alternatively as shown in Figure 1 below.
Hence, we can arrange the roses only in one way.
Case 2: Two blue roses are togetherWe can select two roses and place them together. Once, done, the three red roses can be placed as shown in Figures 2(a) and 2(b).
The third blue rose can be placed either in position 2(a) or in position 2(b).
Hence, we can arrange the roses only in two ways.
Case 3: Three blue roses are togetherIn this arrangement, roses of the same kind are placed together as shown in Figure 3.
Hence, we can arrange the roses only in one way.
Total way of arranging the roses = 1 + 2 + 1 = 4
IMO CP.S. - If someone knows a more direct method of solving such questions do share. I am wondering what if the number of roses was large.
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