Finding the Fourth Proportional to 1,036.72, 1,430.16 and 643.12

Step by Step Solution

1. Step 1: Write the proportion equation
   1,036.72 : 1,430.16 = 643.12 : x
2. Step 2: Convert to fraction form
   1,036.72/1,430.16 = 643.12/x
3. Step 3: Cross multiply
   1,036.72x = 1,430.16 × 643.12
4. Step 4: Simplify right side
   1,036.72x = 919,764.50
5. Step 5: Solve for x
   x = 919,764.50/1,036.72
6. Step 6: Final answer
   x = 887.19