Finding the Fourth Proportional to 3,986.42, 5,978.71 and 1,212.57

Step by Step Solution

1. Step 1: Write the proportion equation
   3,986.42 : 5,978.71 = 1,212.57 : x
2. Step 2: Convert to fraction form
   3,986.42/5,978.71 = 1,212.57/x
3. Step 3: Cross multiply
   3,986.42x = 5,978.71 × 1,212.57
4. Step 4: Simplify right side
   3,986.42x = 7,249,605.90
5. Step 5: Solve for x
   x = 7,249,605.90/3,986.42
6. Step 6: Final answer
   x = 1,818.58