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Question

From the letters of the word BRIGHT, how many 3-letter arrangements can be formed without repeating any letter ?

The correct answer is
120

Solving BRIGHT Word Arrangements

The question asks for the number of distinct 3-letter arrangements that can be formed using the letters from the word "BRIGHT" without allowing any letter to be repeated.

Identifying Key Information

  • The word "BRIGHT" has 6 distinct letters: B, R, I, G, H, T.
  • We need to form arrangements of 3 letters.
  • Repetition of letters is not allowed.

Applying the Permutation Concept

This is a permutation problem because the order of the letters matters in an arrangement. We need to find the number of permutations of 6 distinct items taken 3 at a time.

The formula for permutations is:

$ P(n, r) = \frac{n!}{(n-r)!} $

Where:

  • n is the total number of items to choose from (n=6 letters in "BRIGHT").
  • r is the number of items to arrange (r=3 letters).

Calculation Steps

  1. Substitute the values of n and r into the formula:

    $ P(6, 3) = \frac{6!}{(6-3)!} $

  2. Simplify the denominator:

    $ P(6, 3) = \frac{6!}{3!} $

  3. Expand the factorials:

    $ P(6, 3) = \frac{6 \times 5 \times 4 \times 3 \times 2 \times 1}{3 \times 2 \times 1} $

  4. Cancel out the common terms ($3!$):

    $ P(6, 3) = 6 \times 5 \times 4 $

  5. Calculate the final result:

    $ P(6, 3) = 30 \times 4 = 120 $

Therefore, there are 120 distinct 3-letter arrangements that can be formed from the letters of the word "BRIGHT" without repetition.

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Important Questions from Grouping and Selections

  1. Dates of birth of some persons are given below. Find out the date of birth of the oldest person:

    A. 12.08.1989

    B. 13.09.1991

    C. 19.06.1991

    D. 20.02.1989

    E. 22.03.1991

    F. 20.01.1991

    G. 20.12.1989
  2. Who takes a banana?

    A. Hu

    B. Ku

    C. Moo

    D. Cannot be determined

  3. Which fruit does Ku take?

    A. Orange

    B. Plum

    C. Banana

    D. Mango

  4. Which is the correct combination?

    A. Moo - Banana

    B. Hu - Plum

    C. Hu - Orange

    D. Moo - Plum

  5. In a class of 120 students, 100 students participate in either Golf or Skating or both. Among them, total 60 students participate in Golf. A total of 56 students participate in Skating. How many students participate only in Skating?

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