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Finding the Fourth Proportional to 1,108.75, 1,530.28 and 643

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Solution

The fourth proportional to 1,108.75, 1,530.28 and 643 is: 887.46

Step by Step Solution

  1. Step 1: Write the proportion equation
    1,108.75 : 1,530.28 = 643 : x
  2. Step 2: Convert to fraction form
    1,108.75/1,530.28 = 643/x
  3. Step 3: Cross multiply
    1,108.75x = 1,530.28 × 643
  4. Step 4: Simplify right side
    1,108.75x = 983,970.04
  5. Step 5: Solve for x
    x = 983,970.04/1,108.75
  6. Step 6: Final answer
    x = 887.46

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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.