Finding the Fourth Proportional to 1,388.08, 1,915.68 and 990.46

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.08 : 1,915.68 = 990.46 : x
2. Step 2: Convert to fraction form
   1,388.08/1,915.68 = 990.46/x
3. Step 3: Cross multiply
   1,388.08x = 1,915.68 × 990.46
4. Step 4: Simplify right side
   1,388.08x = 1,897,404.41
5. Step 5: Solve for x
   x = 1,897,404.41/1,388.08
6. Step 6: Final answer
   x = 1,366.93