Finding the Fourth Proportional to 1,005.13, 1,505.59 and 638.10

Step by Step Solution

1. Step 1: Write the proportion equation
   1,005.13 : 1,505.59 = 638.10 : x
2. Step 2: Convert to fraction form
   1,005.13/1,505.59 = 638.10/x
3. Step 3: Cross multiply
   1,005.13x = 1,505.59 × 638.10
4. Step 4: Simplify right side
   1,005.13x = 960,716.98
5. Step 5: Solve for x
   x = 960,716.98/1,005.13
6. Step 6: Final answer
   x = 955.81