Finding the Fourth Proportional to 1,780.67, 2,672.72 and 856.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,780.67 : 2,672.72 = 856.86 : x
2. Step 2: Convert to fraction form
   1,780.67/2,672.72 = 856.86/x
3. Step 3: Cross multiply
   1,780.67x = 2,672.72 × 856.86
4. Step 4: Simplify right side
   1,780.67x = 2,290,146.86
5. Step 5: Solve for x
   x = 2,290,146.86/1,780.67
6. Step 6: Final answer
   x = 1,286.12