Finding the Fourth Proportional to 1,225.59, 1,691.49 and 783.78

Step by Step Solution

1. Step 1: Write the proportion equation
   1,225.59 : 1,691.49 = 783.78 : x
2. Step 2: Convert to fraction form
   1,225.59/1,691.49 = 783.78/x
3. Step 3: Cross multiply
   1,225.59x = 1,691.49 × 783.78
4. Step 4: Simplify right side
   1,225.59x = 1,325,756.03
5. Step 5: Solve for x
   x = 1,325,756.03/1,225.59
6. Step 6: Final answer
   x = 1,081.73