Finding the Fourth Proportional to 1,420.56, 1,959.64 and 978.72

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.56 : 1,959.64 = 978.72 : x
2. Step 2: Convert to fraction form
   1,420.56/1,959.64 = 978.72/x
3. Step 3: Cross multiply
   1,420.56x = 1,959.64 × 978.72
4. Step 4: Simplify right side
   1,420.56x = 1,917,938.86
5. Step 5: Solve for x
   x = 1,917,938.86/1,420.56
6. Step 6: Final answer
   x = 1,350.13