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Finding the Fourth Proportional to 1,109.12, 1,530.78 and 643.40

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Solution

The fourth proportional to 1,109.12, 1,530.78 and 643.40 is: 888.00

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,109.12 : 1,530.78 = 643.40 : x
  2. Step 2: Convert to fraction form
    1,109.12/1,530.78 = 643.40/x
  3. Step 3: Cross multiply
    1,109.12x = 1,530.78 × 643.40
  4. Step 4: Simplify right side
    1,109.12x = 984,903.85
  5. Step 5: Solve for x
    x = 984,903.85/1,109.12
  6. Step 6: Final answer
    x = 888.00

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Why These Related Problems?

These problems maintain the same ratio (1.38) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.