Finding the Fourth Proportional to 21,128.07, 31,686.91 and 7,087.78

Step by Step Solution

1. Step 1: Write the proportion equation
   21,128.07 : 31,686.91 = 7,087.78 : x
2. Step 2: Convert to fraction form
   21,128.07/31,686.91 = 7,087.78/x
3. Step 3: Cross multiply
   21,128.07x = 31,686.91 × 7,087.78
4. Step 4: Simplify right side
   21,128.07x = 224,589,789.70
5. Step 5: Solve for x
   x = 224,589,789.70/21,128.07
6. Step 6: Final answer
   x = 10,629.93