Finding the Fourth Proportional to 1,391.20, 1,919.91 and 761.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.20 : 1,919.91 = 761.72 : x
2. Step 2: Convert to fraction form
   1,391.20/1,919.91 = 761.72/x
3. Step 3: Cross multiply
   1,391.20x = 1,919.91 × 761.72
4. Step 4: Simplify right side
   1,391.20x = 1,462,433.85
5. Step 5: Solve for x
   x = 1,462,433.85/1,391.20
6. Step 6: Final answer
   x = 1,051.20