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The mean of five observations… (Class 10 Maths 2024, Q16)

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MathsCBSE Class 10 · Standard · Board exam 2024, set 30/3/1 · 1 mark · MCQ

CBSE Class 10 Mathematics Standard 2024: question 16

Set in the CBSE Class 10 board exam of 2024, paper 30/3/1, section A, question 16, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q16 · 1 mark · MCQStatistics

The mean of five observations is 15. If the mean of first three observations is 14 and that of the last three observations is 17, then the third observation is

  1. (A)20
  2. (B)19
  3. (C)18
  4. (D)17

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 30/3/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Convert each mean into a sum.

Hint 2

The third observation appears in both groups of three.

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Sum of all five . Sum of the first three and sum of the last three .

  2. The third observation is counted twice: , so . This is option (C).

    1 mark

Answer: 18, option (C)

Where the marks are

  • Uses the overlap of sums to get 18, option (C) (1 mark)

Revise the chapter

  • Chapter: Statistics (notes, formulas, where marks are lost and every past question)
Practise this chapterBoard-style questions from Statistics, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 30/3/1 (Standard): every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.