Home / 13.21-19.80-12.78

Finding the Fourth Proportional to 13.21, 19.80 and 12.78

Calculator

Solution

The fourth proportional to 13.21, 19.80 and 12.78 is: 19.16

Step by Step Solution

  1. Step 1: Write the proportion equation
    13.21 : 19.80 = 12.78 : x
  2. Step 2: Convert to fraction form
    13.21/19.80 = 12.78/x
  3. Step 3: Cross multiply
    13.21x = 19.80 × 12.78
  4. Step 4: Simplify right side
    13.21x = 253.04
  5. Step 5: Solve for x
    x = 253.04/13.21
  6. Step 6: Final answer
    x = 19.16

Related Problems

Find fourth proportional to 6.61, 9.90 and 6.39
Half scale
Find fourth proportional to 26.42, 39.60 and 25.56
Double scale
Find fourth proportional to 14.21, 21.30 and 13.78
Similar ratio
Find fourth proportional to 19.82, 29.70 and 19.17
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.