A shop of electronic goods is closed on Monday. The average daily sales for remaining six days of a week is ₹ 15,640/- and the average sale of Tuesday to Saturday is ₹ 14,124/-. The sales on Sunday is

### Concept & Strategy This problem uses the concept of finding a missing value by subtracting a subset total from an overall total. $$\text{Total Value} = \text{Average} \times \text{Number of Entities}$$ If we know the total sales for 6 days and the total sales for 5 of those days, the difference is exactly the sales of the 6th day (Sunday). ### Step-by-Step Solution * **Calculation (Total 6 days):** Find the total sales for the 6 open days (Tuesday through Sunday). Total for 6 days = $6 \times 15640$ Total for 6 days = 93840 * **Calculation (Total 5 days):** Find the total sales for the 5 days from Tuesday to Saturday. Total for 5 days = $5 \times 14124$ Total for 5 days = 70620 * **Deduction (Sunday):** Subtract the 5-day total from the 6-day total to isolate Sunday's sales. Sunday Sales = (Total for 6 days) - (Total for 5 days) Sunday Sales = $93840 - 70620$ Sunday Sales = 23220 ### Exam Strategy & Shortcut **Unit Digit Method:** You don't necessarily have to calculate the full multiplication. Check the unit digit of the 6-day sum: $6 \times 0 = 0$. Check the unit digit of the 5-day sum: $5 \times 4 = 20 \rightarrow$ ends in 0. This doesn't help much since all options (except Data inadequate) end in something else, wait! Let's look at the last *two* digits. Last two digits of $6 \times 40 = 240 \rightarrow 40$. Last two digits of $5 \times 24 = 120 \rightarrow 20$. The difference in the last two digits is $40 - 20 = 20$. Looking at the options, only ₹ 23,220/- ends with 20. You can select it immediately without full multiplication! ### Common Pitfall Students might get confused by the "closed on Monday" detail and try to divide by 7 at some point, or mistakenly assume Monday counts as a zero in an average of 7 days. The problem explicitly restricts the averages to the "remaining six days", so Monday is irrelevant. ### Final Answer **Therefore, the correct answer is ₹ 23,220/-.**