Finding the Fourth Proportional to 21,279.56, 31,919.30 and 12,847.74

Step by Step Solution

1. Step 1: Write the proportion equation
   21,279.56 : 31,919.30 = 12,847.74 : x
2. Step 2: Convert to fraction form
   21,279.56/31,919.30 = 12,847.74/x
3. Step 3: Cross multiply
   21,279.56x = 31,919.30 × 12,847.74
4. Step 4: Simplify right side
   21,279.56x = 410,090,899.50
5. Step 5: Solve for x
   x = 410,090,899.50/21,279.56
6. Step 6: Final answer
   x = 19,271.59