Official Solution:What is the sum of all common positive factors of 48 and 36? A. 22
B. 24
C. 26
D. 27
E. 28
Step 1: Find the greatest common divisor (GCD) of 48 and 36.
• Why start with the GCD? The GCD of two numbers is the largest number that divides both of them without leaving a remainder. As such, all the positive factors of the GCD will also be common factors of the two numbers.
The GCD of \(48 = 2^4*3\) and \(36 = 2^2*3^2\) is \(2^2*3 = 12\).
Step 2: Find the positive factors of 12.
The positive factors are: 1, 2, 3, 4, 6, and 12.
Step 3: Sum up the factors.
\(1 + 2 + 3 + 4 + 6 + 12 = 28\).
Therefore, the sum of all common positive factors of 48 and 36 is 28.
Answer: E