Home / 639.40-882.20-390.63

Finding the Fourth Proportional to 639.40, 882.20 and 390.63

Calculator

Solution

The fourth proportional to 639.40, 882.20 and 390.63 is: 538.97

Step by Step Solution

  1. Step 1: Write the proportion equation
    639.40 : 882.20 = 390.63 : x
  2. Step 2: Convert to fraction form
    639.40/882.20 = 390.63/x
  3. Step 3: Cross multiply
    639.40x = 882.20 × 390.63
  4. Step 4: Simplify right side
    639.40x = 344,614.76
  5. Step 5: Solve for x
    x = 344,614.76/639.40
  6. Step 6: Final answer
    x = 538.97

Related Problems

Find fourth proportional to 319.70, 441.10 and 195.32
Half scale
Find fourth proportional to 1,278.80, 1,764.41 and 781.26
Double scale
Find fourth proportional to 640.40, 883.58 and 391.63
Similar ratio
Find fourth proportional to 959.10, 1,323.30 and 585.95
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.