Finding the Fourth Proportional to 1,109.98, 1,665.64 and 642.05

Step by Step Solution

1. Step 1: Write the proportion equation
   1,109.98 : 1,665.64 = 642.05 : x
2. Step 2: Convert to fraction form
   1,109.98/1,665.64 = 642.05/x
3. Step 3: Cross multiply
   1,109.98x = 1,665.64 × 642.05
4. Step 4: Simplify right side
   1,109.98x = 1,069,420.95
5. Step 5: Solve for x
   x = 1,069,420.95/1,109.98
6. Step 6: Final answer
   x = 963.46