Finding the Fourth Proportional to 31,072.79, 42,865.78 and 21,004.74

Step by Step Solution

1. Step 1: Write the proportion equation
   31,072.79 : 42,865.78 = 21,004.74 : x
2. Step 2: Convert to fraction form
   31,072.79/42,865.78 = 21,004.74/x
3. Step 3: Cross multiply
   31,072.79x = 42,865.78 × 21,004.74
4. Step 4: Simplify right side
   31,072.79x = 900,384,563.80
5. Step 5: Solve for x
   x = 900,384,563.80/31,072.79
6. Step 6: Final answer
   x = 28,976.62