Finding the Fourth Proportional to 1,380.13, 1,904.98 and 820.99

Step by Step Solution

1. Step 1: Write the proportion equation
   1,380.13 : 1,904.98 = 820.99 : x
2. Step 2: Convert to fraction form
   1,380.13/1,904.98 = 820.99/x
3. Step 3: Cross multiply
   1,380.13x = 1,904.98 × 820.99
4. Step 4: Simplify right side
   1,380.13x = 1,563,962.72
5. Step 5: Solve for x
   x = 1,563,962.72/1,380.13
6. Step 6: Final answer
   x = 1,133.20