Finding the Fourth Proportional to 31,104.84, 42,890.78 and 21,015.78

Step by Step Solution

1. Step 1: Write the proportion equation
   31,104.84 : 42,890.78 = 21,015.78 : x
2. Step 2: Convert to fraction form
   31,104.84/42,890.78 = 21,015.78/x
3. Step 3: Cross multiply
   31,104.84x = 42,890.78 × 21,015.78
4. Step 4: Simplify right side
   31,104.84x = 901,383,196.51
5. Step 5: Solve for x
   x = 901,383,196.51/31,104.84
6. Step 6: Final answer
   x = 28,978.87