Finding the Fourth Proportional to 1,388.43, 1,915.65 and 821.16

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.43 : 1,915.65 = 821.16 : x
2. Step 2: Convert to fraction form
   1,388.43/1,915.65 = 821.16/x
3. Step 3: Cross multiply
   1,388.43x = 1,915.65 × 821.16
4. Step 4: Simplify right side
   1,388.43x = 1,573,055.15
5. Step 5: Solve for x
   x = 1,573,055.15/1,388.43
6. Step 6: Final answer
   x = 1,132.97