Finding the Fourth Proportional to 1,388.16, 1,916.22 and 890.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.16 : 1,916.22 = 890.76 : x
2. Step 2: Convert to fraction form
   1,388.16/1,916.22 = 890.76/x
3. Step 3: Cross multiply
   1,388.16x = 1,916.22 × 890.76
4. Step 4: Simplify right side
   1,388.16x = 1,706,892.13
5. Step 5: Solve for x
   x = 1,706,892.13/1,388.16
6. Step 6: Final answer
   x = 1,229.61