Finding the Fourth Proportional to 1,392.80, 1,922.76 and 869.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,392.80 : 1,922.76 = 869.12 : x
2. Step 2: Convert to fraction form
   1,392.80/1,922.76 = 869.12/x
3. Step 3: Cross multiply
   1,392.80x = 1,922.76 × 869.12
4. Step 4: Simplify right side
   1,392.80x = 1,671,109.17
5. Step 5: Solve for x
   x = 1,671,109.17/1,392.80
6. Step 6: Final answer
   x = 1,199.82