Finding the Fourth Proportional to 1,145.20, 1,580.72 and 679.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,145.20 : 1,580.72 = 679.72 : x
2. Step 2: Convert to fraction form
   1,145.20/1,580.72 = 679.72/x
3. Step 3: Cross multiply
   1,145.20x = 1,580.72 × 679.72
4. Step 4: Simplify right side
   1,145.20x = 1,074,447.00
5. Step 5: Solve for x
   x = 1,074,447.00/1,145.20
6. Step 6: Final answer
   x = 938.22