csatmedium
A flag has to be designed with 4 horizontal stripes using some or all of the colours red, green and yellow. What is the number of different ways in which this can be done so that no two adjacent stripes have the same colour?
- A.12
- B.18
- C.24
- D.36
▶ Answer & Explanation
Correct answer: C. 24
For the first stripe, there are 3 color choices. For the second stripe, since it cannot be the same color as the first, there are 2 color choices. For the third stripe, it can be any color except the second stripe's color, giving 2 choices. Similarly, for the fourth stripe, there are 2 choices. Thus, the total number of ways is 3 * 2 * 2 * 2 = 24.
Source: UPSC csat 2023