Multiple choice

The average marks obtained by 22 candidates in an examination are 45. The average marks of the first 10 are 55 and those of the last eleven are 40. The number of marks obtained by the eleventh candidate is-

  1. 45

  2. 0

  3. 50

  4. 47.5

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Total marks of 22 candidates = 22 × 45 = 990. Marks of first 10 = 10 × 55 = 550. Marks of last 11 = 11 × 40 = 440. The eleventh candidate is counted in both groups (first 10 and last 11 overlap at candidate 11). Let eleventh candidate's marks = x. Then: (550 - x) + x + (440 - x) = 990 is wrong. Actually: first 10 + last 11 counts eleventh twice, so 550 + 440 - x = 990, giving x = 0. Option B matches.

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