Finding the Fourth Proportional to 1,388.56, 1,916.88 and 1,089.13

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.56 : 1,916.88 = 1,089.13 : x
2. Step 2: Convert to fraction form
   1,388.56/1,916.88 = 1,089.13/x
3. Step 3: Cross multiply
   1,388.56x = 1,916.88 × 1,089.13
4. Step 4: Simplify right side
   1,388.56x = 2,087,726.72
5. Step 5: Solve for x
   x = 2,087,726.72/1,388.56
6. Step 6: Final answer
   x = 1,503.52