A photographer arranges people in a row, but two specific persons refuse to stand next to each other. In how many ways can the arrangement be made?
- A240
- B120
- C720
- D480
Solution & Step-by-step Explanation
To find the number of ways where two persons are not together, we can use the method:
Step 1: Calculate total ways to arrange people in a row:
Step 2: Calculate ways where the two specific persons stand together:
Treat these two persons as a single block/unit. Now we have units to arrange.
Number of ways to arrange units = .
Within the block, the two persons can switch places in ways.
Step 3: Calculate the required ways:
Step 1: Calculate total ways to arrange people in a row:
Step 2: Calculate ways where the two specific persons stand together:
Treat these two persons as a single block/unit. Now we have units to arrange.
Number of ways to arrange units = .
Within the block, the two persons can switch places in ways.
Step 3: Calculate the required ways: