Finding the Fourth Proportional to 1,223.86, 1,687.98 and 830.20

Step by Step Solution

1. Step 1: Write the proportion equation
   1,223.86 : 1,687.98 = 830.20 : x
2. Step 2: Convert to fraction form
   1,223.86/1,687.98 = 830.20/x
3. Step 3: Cross multiply
   1,223.86x = 1,687.98 × 830.20
4. Step 4: Simplify right side
   1,223.86x = 1,401,361.00
5. Step 5: Solve for x
   x = 1,401,361.00/1,223.86
6. Step 6: Final answer
   x = 1,145.03