Finding the Fourth Proportional to 1,369.79, 1,890.65 and 780.51

Step by Step Solution

1. Step 1: Write the proportion equation
   1,369.79 : 1,890.65 = 780.51 : x
2. Step 2: Convert to fraction form
   1,369.79/1,890.65 = 780.51/x
3. Step 3: Cross multiply
   1,369.79x = 1,890.65 × 780.51
4. Step 4: Simplify right side
   1,369.79x = 1,475,667.33
5. Step 5: Solve for x
   x = 1,475,667.33/1,369.79
6. Step 6: Final answer
   x = 1,077.30