Finding the Fourth Proportional to 1,139.74, 1,572.87 and 667.57

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.74 : 1,572.87 = 667.57 : x
2. Step 2: Convert to fraction form
   1,139.74/1,572.87 = 667.57/x
3. Step 3: Cross multiply
   1,139.74x = 1,572.87 × 667.57
4. Step 4: Simplify right side
   1,139.74x = 1,050,000.83
5. Step 5: Solve for x
   x = 1,050,000.83/1,139.74
6. Step 6: Final answer
   x = 921.26