Finding the Fourth Proportional to 2,079.60, 3,117.96 and 780.72

Step by Step Solution

1. Step 1: Write the proportion equation
   2,079.60 : 3,117.96 = 780.72 : x
2. Step 2: Convert to fraction form
   2,079.60/3,117.96 = 780.72/x
3. Step 3: Cross multiply
   2,079.60x = 3,117.96 × 780.72
4. Step 4: Simplify right side
   2,079.60x = 2,434,253.73
5. Step 5: Solve for x
   x = 2,434,253.73/2,079.60
6. Step 6: Final answer
   x = 1,170.54