Finding the Fourth Proportional to 1,388.76, 2,080.86 and 772.68

Step by Step Solution

1. Step 1: Write the proportion equation
   1,388.76 : 2,080.86 = 772.68 : x
2. Step 2: Convert to fraction form
   1,388.76/2,080.86 = 772.68/x
3. Step 3: Cross multiply
   1,388.76x = 2,080.86 × 772.68
4. Step 4: Simplify right side
   1,388.76x = 1,607,838.90
5. Step 5: Solve for x
   x = 1,607,838.90/1,388.76
6. Step 6: Final answer
   x = 1,157.75