Finding the Fourth Proportional to 1,420.66, 1,960.59 and 978.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,420.66 : 1,960.59 = 978.76 : x
2. Step 2: Convert to fraction form
   1,420.66/1,960.59 = 978.76/x
3. Step 3: Cross multiply
   1,420.66x = 1,960.59 × 978.76
4. Step 4: Simplify right side
   1,420.66x = 1,918,947.07
5. Step 5: Solve for x
   x = 1,918,947.07/1,420.66
6. Step 6: Final answer
   x = 1,350.74