Finding the Fourth Proportional to 1,173.89, 1,619.94 and 642.76

Step by Step Solution

1. Step 1: Write the proportion equation
   1,173.89 : 1,619.94 = 642.76 : x
2. Step 2: Convert to fraction form
   1,173.89/1,619.94 = 642.76/x
3. Step 3: Cross multiply
   1,173.89x = 1,619.94 × 642.76
4. Step 4: Simplify right side
   1,173.89x = 1,041,221.32
5. Step 5: Solve for x
   x = 1,041,221.32/1,173.89
6. Step 6: Final answer
   x = 886.99