Finding the Fourth Proportional to 21,005.39, 31,513.56 and 7,858.79

Step by Step Solution

1. Step 1: Write the proportion equation
   21,005.39 : 31,513.56 = 7,858.79 : x
2. Step 2: Convert to fraction form
   21,005.39/31,513.56 = 7,858.79/x
3. Step 3: Cross multiply
   21,005.39x = 31,513.56 × 7,858.79
4. Step 4: Simplify right side
   21,005.39x = 247,658,381.33
5. Step 5: Solve for x
   x = 247,658,381.33/21,005.39
6. Step 6: Final answer
   x = 11,790.23