Finding the Fourth Proportional to 1,139.38, 1,572.65 and 667.35

Step by Step Solution

1. Step 1: Write the proportion equation
   1,139.38 : 1,572.65 = 667.35 : x
2. Step 2: Convert to fraction form
   1,139.38/1,572.65 = 667.35/x
3. Step 3: Cross multiply
   1,139.38x = 1,572.65 × 667.35
4. Step 4: Simplify right side
   1,139.38x = 1,049,507.14
5. Step 5: Solve for x
   x = 1,049,507.14/1,139.38
6. Step 6: Final answer
   x = 921.12