Formula 1

Average = sum of observation % number of observation

💡 Important Properties:

  1. If each term is increased or decreased by same number x,

    → New Average = Old Average ± x

  2. If each term is multiplied or divided by x,

    → New Average = Old Average × or ÷ x

WEIGHTED & COMBINED AVERAGE

formula

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Formula

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Average of the consecutive number

Average of consecutive numbers = middle number

Example 5:

Numbers: 9, 10, 11

Average = middle = 10

Question

🧩 Q1:

The average age of 40 students is 20 years. When the teacher’s age is added, the average increases by 1 year. Find teacher’s age.

Solution: