Finding the Fourth Proportional to 1,320.69, 1,978.59 and 1,260.75

Step by Step Solution

1. Step 1: Write the proportion equation
   1,320.69 : 1,978.59 = 1,260.75 : x
2. Step 2: Convert to fraction form
   1,320.69/1,978.59 = 1,260.75/x
3. Step 3: Cross multiply
   1,320.69x = 1,978.59 × 1,260.75
4. Step 4: Simplify right side
   1,320.69x = 2,494,507.34
5. Step 5: Solve for x
   x = 2,494,507.34/1,320.69
6. Step 6: Final answer
   x = 1,888.79