Multiple choice

Find the average age of 120 students studying in a class X. Statement I: Average age of boys in class is 17 years and 6 months. Statement II: Average age of girls in class is 15 years and 3 months. Statement III: If 30 new students join the class with an average age of 19 years the new average age of class will increase by 9 months.

  1. Any two are sufficient

  2. III and (I or II) together are sufficient

  3. Only II and III together are sufficient

  4. Only I and II together are sufficient

  5. Other than given options
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

We need to find the average age of 120 students. Statements I and II give average ages of boys and girls separately, but we don't know how many are boys vs girls. Statement III gives that adding 30 new students with average age 19 increases the average by 9 months (0.75 years). This creates an equation: (120A + 30×19)/150 = A + 0.75, which gives A = 16.25 years. Statement III alone is sufficient. The given options don't include 'Only III is sufficient', so 'Other than given options' is correct.

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