Option 1 : 28

**Given:**

Average of 7 numbers = 28

Sum of first two = 2/5 × sum of last five

**Formula used:**

Average = sum of observations/total number of observations

**Calculation:**

Sum of 7 numbers = 7 × 28 = 196

First two numbers : last five numbers = 2 ∶ 5

Total sum = 7 ratio

∴ Sum of last five numbers = 5/7 × 196 = 140

Average = 140/5 = 28

**∴ The average is 28**