Finding the Fourth Proportional to 1,012.95, 1,397.78 and 619.90

Step by Step Solution

1. Step 1: Write the proportion equation
   1,012.95 : 1,397.78 = 619.90 : x
2. Step 2: Convert to fraction form
   1,012.95/1,397.78 = 619.90/x
3. Step 3: Cross multiply
   1,012.95x = 1,397.78 × 619.90
4. Step 4: Simplify right side
   1,012.95x = 866,483.82
5. Step 5: Solve for x
   x = 866,483.82/1,012.95
6. Step 6: Final answer
   x = 855.41