The daily wages of 40 farm workers are grouped below.

Explanation

1. 01

   Class marks: 220, 260, 300, 340, 380. Deviations d from 300: −80, −40, 0, 40, 80.

2. 02

   $\sum fd = 5(-80) + 7(-40) + 0 + 8(40) + 5(80) = -400 - 280 + 320 + 400 = 40$.

3. 03

   Mean = $300 + \frac{40}{40} = 301$.