Finding the Fourth Proportional to 1,389.55, 1,917.58 and 768.55

Step by Step Solution

1. Step 1: Write the proportion equation
   1,389.55 : 1,917.58 = 768.55 : x
2. Step 2: Convert to fraction form
   1,389.55/1,917.58 = 768.55/x
3. Step 3: Cross multiply
   1,389.55x = 1,917.58 × 768.55
4. Step 4: Simplify right side
   1,389.55x = 1,473,752.27
5. Step 5: Solve for x
   x = 1,473,752.27/1,389.55
6. Step 6: Final answer
   x = 1,060.60