Home / 86.78-129.98-70.64

Finding the Fourth Proportional to 86.78, 129.98 and 70.64

Calculator

Solution

The fourth proportional to 86.78, 129.98 and 70.64 is: 105.80

Step by Step Solution

  1. Step 1: Write the proportion equation
    86.78 : 129.98 = 70.64 : x
  2. Step 2: Convert to fraction form
    86.78/129.98 = 70.64/x
  3. Step 3: Cross multiply
    86.78x = 129.98 × 70.64
  4. Step 4: Simplify right side
    86.78x = 9,180.78
  5. Step 5: Solve for x
    x = 9,180.78/86.78
  6. Step 6: Final answer
    x = 105.80

Related Problems

Find fourth proportional to 43.39, 64.99 and 35.32
Half scale
Find fourth proportional to 173.55, 259.95 and 141.27
Double scale
Find fourth proportional to 87.78, 131.47 and 71.64
Similar ratio
Find fourth proportional to 130.16, 194.96 and 105.95
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.