The average age of 10 children is 9 years 9 months. The average age of 9children is 8 years 11 months. What is the age of the tenth child?
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Answer:
17 ³/₁₂ years
Step-by-step explanation:
x₁ + x₂ +...x₁₀ / 10 = 9⁹/₁₂ ------ (1)
x₁ + x₂ +...x₉ / 9 = 8 ¹¹/₁₂ ------- (2)
(1) - (2)
x₁₀ = 10 x 9⁹/₁₂ - 9 x 8 ¹¹/₁₂
= 117/12 x 10 - 107/12 x 9
= 1170 - 963/12
= 207/12
= 17 ³/₁₂ years
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