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Finding the Fourth Proportional to 878.85, 1,211.29 and 642.40

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Solution

The fourth proportional to 878.85, 1,211.29 and 642.40 is: 885.39

Step by Step Solution

  1. Step 1: Write the proportion equation
    878.85 : 1,211.29 = 642.40 : x
  2. Step 2: Convert to fraction form
    878.85/1,211.29 = 642.40/x
  3. Step 3: Cross multiply
    878.85x = 1,211.29 × 642.40
  4. Step 4: Simplify right side
    878.85x = 778,128.06
  5. Step 5: Solve for x
    x = 778,128.06/878.85
  6. Step 6: Final answer
    x = 885.39

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1.5x scale

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.