Home / 521.20-781.80-213.09

Finding the Fourth Proportional to 521.20, 781.80 and 213.09

Calculator

Solution

The fourth proportional to 521.20, 781.80 and 213.09 is: 319.64

Step by Step Solution

  1. Step 1: Write the proportion equation
    521.20 : 781.80 = 213.09 : x
  2. Step 2: Convert to fraction form
    521.20/781.80 = 213.09/x
  3. Step 3: Cross multiply
    521.20x = 781.80 × 213.09
  4. Step 4: Simplify right side
    521.20x = 166,593.76
  5. Step 5: Solve for x
    x = 166,593.76/521.20
  6. Step 6: Final answer
    x = 319.64

Related Problems

Find fourth proportional to 260.60, 390.90 and 106.55
Half scale
Find fourth proportional to 1,042.40, 1,563.60 and 426.18
Double scale
Find fourth proportional to 522.20, 783.30 and 214.09
Similar ratio
Find fourth proportional to 781.80, 1,172.70 and 319.64
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.