Question

A house is fitted with ten lamps of each 60 watt. If each lamp burns for 5 hours a
day on an average, find the cost of consumption in a month of 30 days at 80 paise
per unit
a) 72.00
b) 62.00
c) 82.00
d) 92.00​

Answer 1

Answer:

• Cost of energy consumption for 30 days = 72.00 Rs

Explanation:

Given

• Number of lamps in the house = 10 lamps
• Power rating of each lamp, P = 60 W
• Time for which lamps burn each day, t = 5 hrs
• Number of days for which lamps are used = 30 days
• Rate of consumption electricity = 80 Paise per unit

To find

• Cost for electricity consumption in 30 days =?

Formula required

• Formula to calculate Electrical Energy

      Energy = Power · time

[ electrical energy is given by the product of electrical power and time ]

Solution

• Calculating the total power of 10 lamps in the house

→ Total power = 10 × ( power rating of each bulb )

→ Total power = 10 × 60 W

→ Total power = 600 W

• Calculating total time for which 10 lamps are used

→ Total time = ( no. of days ) × ( no. of hours lamps used daily )

→ Total time = 30 × 5 hrs

→ Total time = 150 hrs

• Calculating total energy consumed in 30 days

→ Total energy consumed = ( total power ) × ( total time )

→ Total energy consumed = 600 W × 150 h

→ Total energy consumed = 90,000 Wh

→ Total energy consumed = 90 kWh

[ since, 1 unit electrical energy = 1 kWh therefore]

→ Total energy consumed = 90 units

• Calculating cost of consumption of energy in 30 days

→ Cost of energy consumption = ( rate per unit of energy) × ( electrical energy consumed )

→ Cost of energy consumption = ( 80 paise ) × ( 90 units of energy )

→ Cost of energy consumed = 7200 Paise

[ since, 1 Rs = 100 Paise therefore, ]

→ Cost of energy consumption = 72.00 Rs.

Answer 2

$\huge\bf{\underline{\underline{\gray{GIVEN:-}}}}$

• A house is fitted with ten lamps of each 60watt .

• Each lamp burns for 5 hrs a day on an average .

$\huge\bf{\underline{\underline{\gray{TO\:FIND:-}}}}$

• The cost of consumption in a month of 30 days .

$\huge\bf{\underline{\underline{\gray{SOLUTION:-}}}}$

✞︎ Total energy spent is given by,

✯ $\bf\pink{E\:=\:n\:E'\:}$

Where,

• $\bf\red{n}$ = Number of bulbs .

• $\bf\red{E'}$ = Energy spent by each bulb .

☯︎ According to the question,

• $\bf\red{n}$ = 10

✞︎ We know that,

$\blue\bigstar\:\bf{\red{\overbrace{\underbrace{\purple{E'\:=\:Power\times{time}\:}}}}}$

$\bf{:\implies\:E'\:=\:(60\times{5}\times{30})\:W.h\:}$

✫ Now total energy spent is,

$\rm{{\orange{:\implies}}\:E\:=\:10\times{60}\times{5}\times{30}\:}$

$\rm{{\green{:\implies}}\:E\:=\:10\times{9000}\:}$

$\bf{{\orange{:\implies}}\:\blue{E\:=\:90\:KW.h}\:}$

☯︎ According to the question,

• Cost per unit is "80 paisa" or "Rs.0.8" .

⇢Cost for 30 days = 90 × 0.8

⇢Cost for 30 days = Rs.72

$\huge\red\therefore$ [a] The cost of consumption in a month of 30 days is "Rs.72" .