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Finding the Fourth Proportional to 861.05, 1,290.36 and 428.51

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Solution

The fourth proportional to 861.05, 1,290.36 and 428.51 is: 642.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    861.05 : 1,290.36 = 428.51 : x
  2. Step 2: Convert to fraction form
    861.05/1,290.36 = 428.51/x
  3. Step 3: Cross multiply
    861.05x = 1,290.36 × 428.51
  4. Step 4: Simplify right side
    861.05x = 552,937.00
  5. Step 5: Solve for x
    x = 552,937.00/861.05
  6. Step 6: Final answer
    x = 642.16

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1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.50) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.