What is the average percentage profit earned by the company B ?

The average (or arithmetic mean) of a set of n values equals the sum of all the values divided by n. Here, Company B's profit percentage for each of the five years (2011-2015) is already given as data in the table, so no fresh computation using the profit formula (Income - Expenditure)/Expenditure x 100 is required - only Company B's five percentage figures need to be averaged.

1. List Company B's profit percentage for every year from the table: 2011 = 30%, 2012 = 40%, 2013 = 35%, 2014 = 50%, 2015 = 35%.

2. Add the five percentages: 30 + 40 + 35 + 50 + 35 = 190.

3. Divide the total by the number of years, 5: 190 / 5 = 38%.

Since all five yearly figures for Company B lie between 30% and 50%, a correctly computed average must also fall in that range, and 38% does. Grouping the same five numbers in a different order - (30 + 50) + (40 + 35 + 35) = 80 + 110 = 190 - reproduces the identical total, confirming the sum and hence the 38% average.