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Finding the Fourth Proportional to 784.90, 1,178.70 and 420.40

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Solution

The fourth proportional to 784.90, 1,178.70 and 420.40 is: 631.32

Step by Step Solution

  1. Step 1: Write the proportion equation
    784.90 : 1,178.70 = 420.40 : x
  2. Step 2: Convert to fraction form
    784.90/1,178.70 = 420.40/x
  3. Step 3: Cross multiply
    784.90x = 1,178.70 × 420.40
  4. Step 4: Simplify right side
    784.90x = 495,525.48
  5. Step 5: Solve for x
    x = 495,525.48/784.90
  6. Step 6: Final answer
    x = 631.32

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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.