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Finding the Fourth Proportional to 78.64, 108.40 and 56.80

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Solution

The fourth proportional to 78.64, 108.40 and 56.80 is: 78.30

Step by Step Solution

  1. Step 1: Write the proportion equation
    78.64 : 108.40 = 56.80 : x
  2. Step 2: Convert to fraction form
    78.64/108.40 = 56.80/x
  3. Step 3: Cross multiply
    78.64x = 108.40 × 56.80
  4. Step 4: Simplify right side
    78.64x = 6,157.12
  5. Step 5: Solve for x
    x = 6,157.12/78.64
  6. Step 6: Final answer
    x = 78.30

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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.