Finding the Fourth Proportional to 1,370.17, 1,890.57 and 780.69

Step by Step Solution

1. Step 1: Write the proportion equation
   1,370.17 : 1,890.57 = 780.69 : x
2. Step 2: Convert to fraction form
   1,370.17/1,890.57 = 780.69/x
3. Step 3: Cross multiply
   1,370.17x = 1,890.57 × 780.69
4. Step 4: Simplify right side
   1,370.17x = 1,475,949.09
5. Step 5: Solve for x
   x = 1,475,949.09/1,370.17
6. Step 6: Final answer
   x = 1,077.20