Finding the Fourth Proportional to 1,187.39, 1,638.60 and 663.42

Step by Step Solution

1. Step 1: Write the proportion equation
   1,187.39 : 1,638.60 = 663.42 : x
2. Step 2: Convert to fraction form
   1,187.39/1,638.60 = 663.42/x
3. Step 3: Cross multiply
   1,187.39x = 1,638.60 × 663.42
4. Step 4: Simplify right side
   1,187.39x = 1,087,080.01
5. Step 5: Solve for x
   x = 1,087,080.01/1,187.39
6. Step 6: Final answer
   x = 915.52