Finding the Fourth Proportional to 1,369.65, 1,889.69 and 780.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,369.65 : 1,889.69 = 780.15 : x
2. Step 2: Convert to fraction form
   1,369.65/1,889.69 = 780.15/x
3. Step 3: Cross multiply
   1,369.65x = 1,889.69 × 780.15
4. Step 4: Simplify right side
   1,369.65x = 1,474,237.75
5. Step 5: Solve for x
   x = 1,474,237.75/1,369.65
6. Step 6: Final answer
   x = 1,076.36