The multi-layered pie-chart below shows the sales of LED television sets for a big retail electronics outlet during 2016 and 2017. The outer layer shows the monthly sales during this period, with each label showing the month followed by sales figure of that month. For some months, the sales figures are not given in the chart. The middle-layer shows quarter-wise aggregate sales figures (in some cases, aggregate quarter-wise sales numbers are not given next to the quarter). The innermost layer shows annual sales. It is known that the sales figures during the three months of the second quarter (April, May, June) of 2016 form an arithmetic progression, as do the three monthly sales figures in the fourth quarter (October, November, December) of that year.
Question:
During which month was the percentage increase in sales from the previous month’s sales the highest?
March of 2017
October of 2017
October of 2016
March of 2016
Let the sales figures for April, May, and June 2016 be a, b, and c, respectively.
We know that these sales figures form an arithmetic sequence, so we have the equation
where d is the common difference.
We also know that the average sales figure for this quarter is 150, so we have the equation:
Substituting the 1st equation into the 2nd equation, we get:
Simplifying this equation, we get:
We can solve this equation for a to get
Substituting this value into the first equation, we get
Since the average sales figure for October, November, and December 2016 is also 150, we have the equation:
Simplifying this equation, we get:
Solving this equation for d, we get
Therefore, the sales figures for April, May, and June 2016 are 40, 50, and 60, respectively.
The sales figures for October, November, and December 2016 are 100, 120, and 140, respectively.
2016 | 2017 | ||||
Quarter | Month | Sale figure | Quarter | Month | Sale figure |
Q1 (240) | January | 80 | Q1(380) | January | 120 |
February | 60 | February | 100 | ||
March | 100 | March | 160 | ||
Q2(150) | April | 40 | Q2(200) | April | 60 |
May | 50 | May | 75 | ||
June | 60 |
|
65 | ||
Q3(250) | July | 75 | Q3(220) | July | 60 |
August | 120 | August | 90 | ||
September | 55 | September | 70 | ||
Q4(360) | October | 100 | Q4(500) | October | 150 |
November | 120 | November | 170 | ||
December | 140 | December | 180 |
Considering all the options:
Sales in March of 2017 = 160
Sales in February of 2017 = 100
increase
Sales in October of 2017 = 150
Sales in September of 2017 = 70
increase
Sales in March of 2016 = 100
Sales in February of 2016 = 60
increase
Sales in October of 2016 = 100
Sales in September of 2016 = 55
increase
Therefore, %increase in sales for option B is highest.