The electricity bill of a certain establishment is partially fixed and partially varies as the number of units of electricity consumed. When in a certain month 540 units are consumed, the bill is Tk. 1800. In another month 620 units are consumed and the bill is Tk 2040. In yet another month if 500 units are consumed what would be the bill (in Tk) for that month?
Solution
Correct Answer: Option D
মনেকরে,
নির্ধারিত সর্বনিম্ম চার্জের পরিমান = x টাকা।
এবং প্রতি ইউনিট বিদ্যুতের দাম = y টাকা।
প্রশ্নমতে,
540y + x = 1800 ...(i) and
620y + x = 2040 ...(ii)
On subtracting (i) from (ii), we get 80y = 240
⇒ y = 3
Putting y = 3 in (i), we get :
540×3 + x = 1800
⇒ x = (1800 − 1620) = 180
∴ Fixed charges = Tk. 180, and, charge per unit = Tk. 3
Total charges for consuming 500 units = Tk. (180 + 500×3) = Tk. 1680
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