Finding the Fourth Proportional to 1,421.72, 1,961.23 and 978.86

Step by Step Solution

1. Step 1: Write the proportion equation
   1,421.72 : 1,961.23 = 978.86 : x
2. Step 2: Convert to fraction form
   1,421.72/1,961.23 = 978.86/x
3. Step 3: Cross multiply
   1,421.72x = 1,961.23 × 978.86
4. Step 4: Simplify right side
   1,421.72x = 1,919,757.34
5. Step 5: Solve for x
   x = 1,919,757.34/1,421.72
6. Step 6: Final answer
   x = 1,350.30