Finding the Fourth Proportional to 1,978.24, 2,965.78 and 991.40

Step by Step Solution

1. Step 1: Write the proportion equation
   1,978.24 : 2,965.78 = 991.40 : x
2. Step 2: Convert to fraction form
   1,978.24/2,965.78 = 991.40/x
3. Step 3: Cross multiply
   1,978.24x = 2,965.78 × 991.40
4. Step 4: Simplify right side
   1,978.24x = 2,940,274.29
5. Step 5: Solve for x
   x = 2,940,274.29/1,978.24
6. Step 6: Final answer
   x = 1,486.31