Finding the Fourth Proportional to 1,111.84, 1,668.72 and 428.32

Step by Step Solution

1. Step 1: Write the proportion equation
   1,111.84 : 1,668.72 = 428.32 : x
2. Step 2: Convert to fraction form
   1,111.84/1,668.72 = 428.32/x
3. Step 3: Cross multiply
   1,111.84x = 1,668.72 × 428.32
4. Step 4: Simplify right side
   1,111.84x = 714,746.15
5. Step 5: Solve for x
   x = 714,746.15/1,111.84
6. Step 6: Final answer
   x = 642.85