Finding the Fourth Proportional to 1,378.81, 1,902.12 and 818.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,378.81 : 1,902.12 = 818.89 : x
2. Step 2: Convert to fraction form
   1,378.81/1,902.12 = 818.89/x
3. Step 3: Cross multiply
   1,378.81x = 1,902.12 × 818.89
4. Step 4: Simplify right side
   1,378.81x = 1,557,627.05
5. Step 5: Solve for x
   x = 1,557,627.05/1,378.81
6. Step 6: Final answer
   x = 1,129.69