Finding the Fourth Proportional to 1,012.89, 1,398.15 and 619.95

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.89 : 1,398.15 = 619.95 : x
2. Step 2: Convert to fraction form
   1,012.89/1,398.15 = 619.95/x
3. Step 3: Cross multiply
   1,012.89x = 1,398.15 × 619.95
4. Step 4: Simplify right side
   1,012.89x = 866,783.09
5. Step 5: Solve for x
   x = 866,783.09/1,012.89
6. Step 6: Final answer
   x = 855.75