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Finding the Fourth Proportional to 715.80, 987.75 and 421.05

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Solution

The fourth proportional to 715.80, 987.75 and 421.05 is: 581.02

Step by Step Solution

  1. Step 1: Write the proportion equation
    715.80 : 987.75 = 421.05 : x
  2. Step 2: Convert to fraction form
    715.80/987.75 = 421.05/x
  3. Step 3: Cross multiply
    715.80x = 987.75 × 421.05
  4. Step 4: Simplify right side
    715.80x = 415,892.14
  5. Step 5: Solve for x
    x = 415,892.14/715.80
  6. Step 6: Final answer
    x = 581.02

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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.