Central Tendency & DispersionPYQ June 24 Series IIQuestion 2933 of 473
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The average age of 15 students is 15 years. Out of these the average age of 5 students is 14 years and that of other 9 students is 16 years, then the age of 15th student is ____.

Options

A11 years
B14 years
C15 years
DNone of these
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Correct Answer

✅ Option a — 11 years

All Options:

  • A11 years
  • B14 years
  • C15 years
  • DNone of these

Detailed Solution & Explanation

We are given: - Total number of students: N=15\displaystyle N = 15 - Average age of all 15 students: xˉ=15\displaystyle \bar{x} = 15 years - Sum of ages of all 15 students: Sumtotal=15×15=225\displaystyle \text{Sum}_{\text{total}} = 15 \times 15 = 225 years - Number of students in the first group: n1=5\displaystyle n_1 = 5 - Average age of this group: xˉ1=14\displaystyle \bar{x}_1 = 14 years - Sum of ages of this group: Sum5=5×14=70\displaystyle \text{Sum}_5 = 5 \times 14 = 70 years - Number of students in the second group: n2=9\displaystyle n_2 = 9 - Average age of this group: xˉ2=16\displaystyle \bar{x}_2 = 16 years - Sum of ages of this group: Sum9=9×16=144\displaystyle \text{Sum}_9 = 9 \times 16 = 144 years - Total number of students accounted for: 5+9=14\displaystyle 5 + 9 = 14 students - Combined sum of ages of these 14 students: Sum14=70+144=214\displaystyle \text{Sum}_{14} = 70 + 144 = 214 years We can find the age of the 15th student by subtracting the sum of the ages of the 14 students from the total sum of the ages of the 15 students: Age15th=Sumtotal−Sum14=225−214=11 years\text{Age}_{15\text{th}} = \text{Sum}_{\text{total}} - \text{Sum}_{14} = 225 - 214 = 11\text{ years} Hence, **Option A** is the correct answer.

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