Question

Compact fluorescent lamps (CFLs) consume one-fourth of electricity than consumed by incandescent
bulbs and CFLs last eight times longer than incandescent bulbs. If the electricity consumed by a household
using incandescent bulbs is 820 units at the rate of ₹4.50 per unit, then answer the following questions
(MCQs – multiple choice questions):-
a) How many units of electricity will be consumed if all bulbs are changed to CFLs?
i. 840 units
ii. 120 units
iii. 210 units
iv. 205 units
b) The amount to be paid when incandescent bulbs are used is
i. ₹4.50
ii. ₹3690
iii. ₹36900
iv. ₹369
c) What is the ratio of units consumed when incandescent bulbs are used to units consumed when CFLs
are used?
i. 160 : 81
ii. 81 : 160
iii. 1 : 4
iv. 4 : 1

Answer 1

Answer:

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Answer 2

Answer:

a. 205 units

b. ₹ 3690

c. 4:1

given,

• Compact fluorescent lamps (CFLs) consume one-fourth of electricity than consumed by incandescent bulbs.
• CFLs last eight times longer than incandescent bulbs.
• electricity consumed by a household using incandescent bulbs is 820 units at the rate of ₹4.50

to find,

1. units of electricity will be consumed if all bulbs are changed to CFLs
2. amount to be paid when incandescent bulbs are used is
3. ratio of units consumed when incandescent bulbs are used to units consumed when CFLs are used.

solution,

1. )

to find the units of electricity will be consumed if all bulbs are changed to CFLs, we must find the ratio of consumption of electricity of both bulbs.

We know that CFLs consume one-fourth of electricity than consumed by incandescent bulbs.

so ratio of consumption of CFL to incandescent bulbs = 1:4.

Let the multiplying factor be Xelectricity consumed by a household using incandescent bulbs = 820

4X = 820

X = 205

consumption of CFL= 1X

consumption of CFL= 1× 205 = 205 units.

2.)

amount to be paid when incandescent bulbs are used- let the amount of electricity bill be Y.

Y = no. of units× price per unit

Y = 820× 4.5

Y= ₹ 3690

3.)

ratio of units consumed when incandescent bulbs are used to units consumed when CFLs are used-

given that electricity consumed by a household using incandescent bulbs = 820

and, we have calculated that consumption of CFL= 205 units

so, the ratio of units consumed when incandescent bulbs are used to when CFLs are used

= 820: 205

= 4:1

Therefore the required answers are :

a. 205 units

b. ₹ 3690

c. 4:1

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