Finding the Fourth Proportional to 20,985.32, 31,488.53 and 13,085.79

Step by Step Solution

1. Step 1: Write the proportion equation
   20,985.32 : 31,488.53 = 13,085.79 : x
2. Step 2: Convert to fraction form
   20,985.32/31,488.53 = 13,085.79/x
3. Step 3: Cross multiply
   20,985.32x = 31,488.53 × 13,085.79
4. Step 4: Simplify right side
   20,985.32x = 412,052,225.56
5. Step 5: Solve for x
   x = 412,052,225.56/20,985.32
6. Step 6: Final answer
   x = 19,635.27