The rate of electricity charge on consumption of less than 150 units are as follows: Rs. 7.30 per unit for
50 units and Rs. 8.60 per unit for 51-150 units. How
many units can be consumed by Rs 1139?
​

140 units

Step-by-step explanation:

Our first task is to determine the amount left for electricity consumption after having bought the first 50 units at Rs. 7.30 per unit

Cost of first 50 units:

1unit=Rs. 7.30

50 units=Rs. 7.30*50

50 units=Rs.365

Amount left=total amount-cost of 50 units

total amount for consumption=Rs 1139

Amount left=Rs 1139-Rs.365

Amount left=Rs 774

Units consumable with the balance=Rs 774/Rs. 8.60

Units consumable with the balance=90 units

Units that can be consumed with Rs 1139=50 units+90 units

Units that can be consumed with Rs 1139=140 units

to find the unit price, we must figure out the cost of one item (in this case one dish towel).   to do this, we divide the total price ($7.92) by the number of items bought (for this problem it is 8, because there are eight dish towels in one pack).  

$7.92/8 = $0.99

therefore, the unit price, or the price of one dish towel, is $0.99.

hope this !