Finding the Fourth Proportional to 1,871.81, 2,807.71 and 831.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,871.81 : 2,807.71 = 831.57 : x
2. Step 2: Convert to fraction form
   1,871.81/2,807.71 = 831.57/x
3. Step 3: Cross multiply
   1,871.81x = 2,807.71 × 831.57
4. Step 4: Simplify right side
   1,871.81x = 2,334,807.40
5. Step 5: Solve for x
   x = 2,334,807.40/1,871.81
6. Step 6: Final answer
   x = 1,247.35