Home / 421.40-628.16-420.80

Finding the Fourth Proportional to 421.40, 628.16 and 420.80

Calculator

Solution

The fourth proportional to 421.40, 628.16 and 420.80 is: 627.25

Step by Step Solution

  1. Step 1: Write the proportion equation
    421.40 : 628.16 = 420.80 : x
  2. Step 2: Convert to fraction form
    421.40/628.16 = 420.80/x
  3. Step 3: Cross multiply
    421.40x = 628.16 × 420.80
  4. Step 4: Simplify right side
    421.40x = 264,324.48
  5. Step 5: Solve for x
    x = 264,324.48/421.40
  6. Step 6: Final answer
    x = 627.25

Related Problems

Find fourth proportional to 210.70, 314.08 and 210.40
Half scale
Find fourth proportional to 842.81, 1,256.31 and 841.59
Double scale
Find fourth proportional to 422.40, 629.65 and 421.80
Similar ratio
Find fourth proportional to 632.10, 942.23 and 631.19
1.5x scale

Why These Related Problems?

These problems maintain the same ratio (1.49) or explore similar proportional relationships. Practicing with related ratios helps build understanding of proportional relationships.