Answer:
Cost = 1333.2[rupees]
Explanation:
We can solve this problem by using unit analysis of quantities, in this way we have:
16 [bulbs] * 40 [watts] = 640 [watts]
1 [bulb] * 100 [watts] = 100 [watts]
Now for each power and its time of working.
[tex]640[w]*\frac{6 hr}{1day} * 30 [days] = 115200 [w-hr]\\100[w]*\frac{2hr}{1day} * 30[days] = 6000 [w-hr][/tex]
115200 [w*hr] = 115.2[Kw-hr]
6000 [w*hr] = 6[kw-hr]
If the cost is 11 rupees/1[kw-hr], then we have
115.2 + 6 = 121.2 [kw-hr]
Cost = 121.2 [kw-hr] * 11 rupees/1 [kw-hr]
Cost = 1333.2 [rupees]
