Finding the Fourth Proportional to 31,015.10, 42,813 and 21,987.65

Step by Step Solution

1. Step 1: Write the proportion equation
   31,015.10 : 42,813 = 21,987.65 : x
2. Step 2: Convert to fraction form
   31,015.10/42,813 = 21,987.65/x
3. Step 3: Cross multiply
   31,015.10x = 42,813 × 21,987.65
4. Step 4: Simplify right side
   31,015.10x = 941,357,045.39
5. Step 5: Solve for x
   x = 941,357,045.39/31,015.10
6. Step 6: Final answer
   x = 30,351.58