Finding the Fourth Proportional to 1,440.79, 1,988.15 and 851.21

Step by Step Solution

1. Step 1: Write the proportion equation
   1,440.79 : 1,988.15 = 851.21 : x
2. Step 2: Convert to fraction form
   1,440.79/1,988.15 = 851.21/x
3. Step 3: Cross multiply
   1,440.79x = 1,988.15 × 851.21
4. Step 4: Simplify right side
   1,440.79x = 1,692,326.42
5. Step 5: Solve for x
   x = 1,692,326.42/1,440.79
6. Step 6: Final answer
   x = 1,174.58