Finding the Fourth Proportional to 1,290.69, 1,780.50 and 817.79

Step by Step Solution

1. Step 1: Write the proportion equation
   1,290.69 : 1,780.50 = 817.79 : x
2. Step 2: Convert to fraction form
   1,290.69/1,780.50 = 817.79/x
3. Step 3: Cross multiply
   1,290.69x = 1,780.50 × 817.79
4. Step 4: Simplify right side
   1,290.69x = 1,456,079.55
5. Step 5: Solve for x
   x = 1,456,079.55/1,290.69
6. Step 6: Final answer
   x = 1,128.14