Finding the Fourth Proportional to 1,387.83, 1,915.67 and 828.47

Step by Step Solution

1. Step 1: Write the proportion equation
   1,387.83 : 1,915.67 = 828.47 : x
2. Step 2: Convert to fraction form
   1,387.83/1,915.67 = 828.47/x
3. Step 3: Cross multiply
   1,387.83x = 1,915.67 × 828.47
4. Step 4: Simplify right side
   1,387.83x = 1,587,075.12
5. Step 5: Solve for x
   x = 1,587,075.12/1,387.83
6. Step 6: Final answer
   x = 1,143.57