Finding the Fourth Proportional to 1,379.61, 1,903.91 and 820.15

Step by Step Solution

1. Step 1: Write the proportion equation
   1,379.61 : 1,903.91 = 820.15 : x
2. Step 2: Convert to fraction form
   1,379.61/1,903.91 = 820.15/x
3. Step 3: Cross multiply
   1,379.61x = 1,903.91 × 820.15
4. Step 4: Simplify right side
   1,379.61x = 1,561,482.93
5. Step 5: Solve for x
   x = 1,561,482.93/1,379.61
6. Step 6: Final answer
   x = 1,131.83