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MODEL-815. The average age of 20 boys in a class is 15 years. If tteacher's age is included then the average age isincreased by 2 years. What is the teacher's age? |
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Answer» Answer: The teacher's age is 57 years. Step-by-step explanation: Given that: The average age of 20 boys in a class is 15 years. If the teacher's age is included then the average age is increased by 2 years. To Find: What is the teacher's age? Let us assume: The teacher's age be x years. Formula used: Average = (SUM of observations)/(Number of observations) First find the sum of observations: Average = (Sum of observations)/(Number of observations) ⟶ 15 = (Sum of observations)/(20) ⟶ Sum of observations = 15 × 20 ⟶ Sum of observations = 300 When teacher's age is included: Sum of observations = 300 + x Number of observations = 20 + 1 = 21 Average = 15 + 2 = 17 years Now finding the age of teacher: Average = (Sum of observations)/(Number of observations) Substituting the values. ⇒ 17 = (300 + x)/21 ⇒ 300 + x = 21 × 17 ⇒ 300 + x = 357 ⇒ x = 357 - 300 ⇒ x = 57 ∴ The teacher's age = 57 years. |
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