Finding the Fourth Proportional to 1,124.75, 1,688.00 and 780.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,124.75 : 1,688.00 = 780.50 : x
2. Step 2: Convert to fraction form
   1,124.75/1,688.00 = 780.50/x
3. Step 3: Cross multiply
   1,124.75x = 1,688.00 × 780.50
4. Step 4: Simplify right side
   1,124.75x = 1,317,480.10
5. Step 5: Solve for x
   x = 1,317,480.10/1,124.75
6. Step 6: Final answer
   x = 1,171.35