Multiple choice

The average salary of all staff of a school is rupees 10000.The average salary of 20 teaching staff is rupees 12000 and that of non-teaching staff is 5,000 the number of non-teaching staff will be

  1. 7

  2. 8

  3. 10

  4. 12
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let x = number of non-teaching staff. Total staff = 20 + x. Overall average = 10000. Total salary = (20+x)×10000. Teaching staff salary = 20×12000 = 240000. Non-teaching salary = x×5000 = 5000x. Total salary also equals 240000 + 5000x. Equating: (20+x)×10000 = 240000 + 5000x. 200000 + 10000x = 240000 + 5000x. 5000x = 40000. x = 8.

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