How many ways can 5 different letters be arranged if 2 letters are always togeth

Practice Questions

Q1
How many ways can 5 different letters be arranged if 2 letters are always together?
  1. 48
  2. 120
  3. 240
  4. 720

Questions & Step-by-Step Solutions

How many ways can 5 different letters be arranged if 2 letters are always together?
  • Step 1: Identify the 5 different letters. Let's call them A, B, C, D, and E.
  • Step 2: Choose the 2 letters that must always be together. For example, let's say we choose A and B.
  • Step 3: Treat the 2 letters (A and B) as one single unit or block. Now, instead of 5 letters, we have 4 units to arrange: (AB), C, D, and E.
  • Step 4: Calculate the number of ways to arrange these 4 units. The formula for arranging n units is n!. So, we calculate 4! (which is 4 factorial).
  • Step 5: Calculate 4! = 4 × 3 × 2 × 1 = 24.
  • Step 6: Now, within the block (AB), the letters A and B can be arranged in 2 ways: AB or BA. This is 2!.
  • Step 7: Calculate 2! = 2 × 1 = 2.
  • Step 8: Multiply the number of arrangements of the 4 units by the arrangements of the letters within the block: 24 (from Step 5) × 2 (from Step 7) = 48.
  • Step 9: Therefore, the total number of ways to arrange the 5 letters with A and B always together is 48.
  • Permutations – The arrangement of objects in a specific order, considering the total number of objects and any constraints.
  • Grouping – Treating a set of items as a single unit to simplify the arrangement process.
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