Q) In a household five fans each of 100W are used for 4 hours and an electric press of 500W for 2 hours every day. Calculate the cost of using the fans and electric press for 60 days if the cost of 1 unit of electrical energy is Rs. 6.5.     

(CBSE Sample Paper – 2024-25)

Ans: 

STEP BY STEP SOLUTION

Let’s first calculate the total energy consumption in a day:

Step 1. Energy consumed by the fans:

Power rating of a fan = 100 w

Usage time: 4 hours / day

∴ Energy consumed by a fan = 100 x 4 = 400 watt hour / day

∴ Energy consumed by 5 fans = 5 x 400 = 2000 watt hour / day

Step 2. Energy consumed by the Electric Press:

Power rating of a Electric Press = 500 w

Usage time: 2 hours / day

∴ Energy consumed by a Electric Press = 500 x 2 = 1000 watt hour / day

Step 3: Total Energy consumption:

Energy consumed by 5 fans and 1 Electric Press

=  Energy consumed by 5 fans + Energy consumed by 1 Electric Press

= 2000 + 1000 = 3000 watt hour / day

Since 1 unit = 1 kwh

∴ The energy consumption / day = 3 units

∴ the energy consumption over 60 days = 3 x 60 = 180 units

Step 4: Cost of energy consumed:

Since the cost of one unit = Rs. 6.50

∴ The cost of 180 units = 180 x 6.50 = Rs. 1,170

Therefore the cost of using 5 fans and 1 electric press over 60 days will be Rs. 1,170.

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