Finding the Fourth Proportional to 1,128.72, 1,557.80 and 663.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,128.72 : 1,557.80 = 663.12 : x
2. Step 2: Convert to fraction form
   1,128.72/1,557.80 = 663.12/x
3. Step 3: Cross multiply
   1,128.72x = 1,557.80 × 663.12
4. Step 4: Simplify right side
   1,128.72x = 1,033,008.34
5. Step 5: Solve for x
   x = 1,033,008.34/1,128.72
6. Step 6: Final answer
   x = 915.20