Finding the Fourth Proportional to 1,319.88, 1,978.58 and 661.34

Step by Step Solution

1. Step 1: Write the proportion equation
   1,319.88 : 1,978.58 = 661.34 : x
2. Step 2: Convert to fraction form
   1,319.88/1,978.58 = 661.34/x
3. Step 3: Cross multiply
   1,319.88x = 1,978.58 × 661.34
4. Step 4: Simplify right side
   1,319.88x = 1,308,514.10
5. Step 5: Solve for x
   x = 1,308,514.10/1,319.88
6. Step 6: Final answer
   x = 991.39