The mean of twelve positive numbers is 3. When another number is added, the mean becomes 5. Find the thirteenth number
A
29
B
26
C
25
D
24
Verified Correct Answer: A.
Step-by-Step Mathematical Solution
Let the sum of the 12 numbers be x and the 13th number be y.
\(\frac{x}{12} = 3 \implies x = 36\)
\(\frac{36 + y}{13} = 5 \implies 36 + y = 65\)
\(y = 65 - 36 = 29\)
Source: Myschool Past Questions Archive (Record #30953)