Finding the Fourth Proportional to 1,391.31, 1,920.01 and 770.31

Step by Step Solution

1. Step 1: Write the proportion equation
   1,391.31 : 1,920.01 = 770.31 : x
2. Step 2: Convert to fraction form
   1,391.31/1,920.01 = 770.31/x
3. Step 3: Cross multiply
   1,391.31x = 1,920.01 × 770.31
4. Step 4: Simplify right side
   1,391.31x = 1,479,009.63
5. Step 5: Solve for x
   x = 1,479,009.63/1,391.31
6. Step 6: Final answer
   x = 1,063.03