Question 1196719
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Hi

μ = 54     σ = 8 
 78 = μ + 3σ    (54 + 24  = 78)
Using the 68-95-99.7 rule
P( 54 ≤ x ≤ 78) = 99.7%/2 = 49.85%

Wish You the Best in your Studies.
 
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