Finding the Fourth Proportional to 13,878.63, 20,815.86 and 5,111.49

Step by Step Solution

1. Step 1: Write the proportion equation
   13,878.63 : 20,815.86 = 5,111.49 : x
2. Step 2: Convert to fraction form
   13,878.63/20,815.86 = 5,111.49/x
3. Step 3: Cross multiply
   13,878.63x = 20,815.86 × 5,111.49
4. Step 4: Simplify right side
   13,878.63x = 106,400,060.23
5. Step 5: Solve for x
   x = 106,400,060.23/13,878.63
6. Step 6: Final answer
   x = 7,666.47