Finding the Fourth Proportional to 1,001.60, 1,380.56 and 780.17

Step by Step Solution

1. Step 1: Write the proportion equation
   1,001.60 : 1,380.56 = 780.17 : x
2. Step 2: Convert to fraction form
   1,001.60/1,380.56 = 780.17/x
3. Step 3: Cross multiply
   1,001.60x = 1,380.56 × 780.17
4. Step 4: Simplify right side
   1,001.60x = 1,077,060.69
5. Step 5: Solve for x
   x = 1,077,060.69/1,001.60
6. Step 6: Final answer
   x = 1,075.35