Finding the Fourth Proportional to 1,075.78, 1,612.71 and 612.89

Step by Step Solution

1. Step 1: Write the proportion equation
   1,075.78 : 1,612.71 = 612.89 : x
2. Step 2: Convert to fraction form
   1,075.78/1,612.71 = 612.89/x
3. Step 3: Cross multiply
   1,075.78x = 1,612.71 × 612.89
4. Step 4: Simplify right side
   1,075.78x = 988,416.35
5. Step 5: Solve for x
   x = 988,416.35/1,075.78
6. Step 6: Final answer
   x = 918.79