Finding the Fourth Proportional to 1,386.57, 2,080.83 and 770.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,386.57 : 2,080.83 = 770.76 : x
2. Step 2: Convert to fraction form
   1,386.57/2,080.83 = 770.76/x
3. Step 3: Cross multiply
   1,386.57x = 2,080.83 × 770.76
4. Step 4: Simplify right side
   1,386.57x = 1,603,820.53
5. Step 5: Solve for x
   x = 1,603,820.53/1,386.57
6. Step 6: Final answer
   x = 1,156.68