Finding the Fourth Proportional to 1,392.38, 1,921.60 and 771.50

Step by Step Solution

1. Step 1: Write the proportion equation
   1,392.38 : 1,921.60 = 771.50 : x
2. Step 2: Convert to fraction form
   1,392.38/1,921.60 = 771.50/x
3. Step 3: Cross multiply
   1,392.38x = 1,921.60 × 771.50
4. Step 4: Simplify right side
   1,392.38x = 1,482,502.86
5. Step 5: Solve for x
   x = 1,482,502.86/1,392.38
6. Step 6: Final answer
   x = 1,064.73