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Shrivathsan
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Power saving of a bulb is directly proportional to square root 04 Sep 2016, 10:41
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65% (02:01) correct 35% (02:16) wrong based on 565 sessions

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Power saving (in %) of a bulb is directly proportional to square root of its efficiency. By how much % is power saving of bulb-1(efficiency 0.8) greater than power saving of bulb-2 (efficiency 0.2)?

A. 60%
B. 70%
C. 80%
D. 90%
E. 100%
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E
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abhimahna
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Power saving of a bulb is directly proportional to square root 04 Sep 2016, 11:11
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Shrivathsan
Power saving (in %) of a bulb is directly proportional to square root of its efficiency. By how much % is power saving of bulb-1(efficiency 0.8) greater than power saving of bulb-2 (efficiency 0.2)?

A. 60%
B. 70%
C. 80%
D. 90%
E. 100%
Show more

Power, \(P1 = k * sqrt(0.8)\)

Power, \(P2 = k * sqrt(0.2)\)

Difference = \(P1-P2 = k * sqrt(0.8) - k * sqrt(0.2)\)

% greater =\(k * sqrt(0.8) - k * sqrt(0.2)/k * sqrt(0.2) * 100\)

= 100%.

Hence, E
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Power saving of a bulb is directly proportional to square root 13 Nov 2017, 10:53
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abhimahna
Shrivathsan
Power saving (in %) of a bulb is directly proportional to square root of its efficiency. By how much % is power saving of bulb-1(efficiency 0.8) greater than power saving of bulb-2 (efficiency 0.2)?

A. 60%
B. 70%
C. 80%
D. 90%
E. 100%

Power, \(P1 = k * sqrt(0.8)\)

Power, \(P2 = k * sqrt(0.2)\)

Difference = \(P1-P2 = k * sqrt(0.8) - k * sqrt(0.2)\)

% greater =\(k * sqrt(0.8) - k * sqrt(0.2)/k * sqrt(0.2) * 100\)

= 100%.

Hence, E
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Can you please elaborate how to simply this.

Quote:
% greater =\(k * sqrt(0.8) - k * sqrt(0.2)/k * sqrt(0.2) * 100\)
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Power saving of a bulb is directly proportional to square root 13 Nov 2017, 11:03
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stne

Can you please elaborate how to simply this.

Quote:
% greater =\(k * sqrt(0.8) - k * sqrt(0.2)/k * sqrt(0.2) * 100\)
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Here I go:

\(sqrt(0.8)\) = sqrt(8)/sqrt(10) = [2*sqrt(2)]/sqrt(10)

\(sqrt(0.2)\) = sqrt(2)/sqrt(10)

You know we can cancel 'k' from denominator and numerator.

Similarly, you have sqrt(10) both at numerator and denominator, so you can cancel that out.

Therefore, you are left with [2*sqrt(2) - sqrt(2) ] / sqrt(2) ] *100 = [sqrt(2) ] / sqrt(2)] *100 = 100%

Does that make sense?
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Power saving of a bulb is directly proportional to square root 20 Feb 2024, 04:29
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You can also multiply by 100 both powers, now you have p1=100*sqrt0.8 and P2=100*sqrt 0.2, P1 is 89 and something while P2 is 45 and something, so the answer is 100%
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Power saving of a bulb is directly proportional to square root 27 Mar 2024, 00:19
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you can simply put it in the following way:

square root of 0.8 --> square root of (2 * 2 * 0.2)

--> 2 square root of 0.2

compared to the second bulb, it's x 2

hence 100% greater
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Power saving of a bulb is directly proportional to square root 07 Jul 2024, 14:26
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Shrivathsan
Power saving (in %) of a bulb is directly proportional to square root of its efficiency. By how much % is power saving of bulb-1(efficiency 0.8) greater than power saving of bulb-2 (efficiency 0.2)?

A. 60%
B. 70%
C. 80%
D. 90%
E. 100%
Show more
­PSB1 = 0.8 = √x --> x ≈ 0.9
PSB2 = 0.2 = √y --> y ≈ 0.45

Percent Greater Than = x - y / y

0.9 - 0.45 / 0.45 = 0.45 / 0.45 = 1 or 100%

 
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Power saving of a bulb is directly proportional to square root Updated on: 29 Jul 2024, 08:21
Originally posted by Purnank on 25 Jul 2024, 00:06.
Last edited by Purnank on 29 Jul 2024, 08:21, edited 1 time in total.
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rebrahimi12

Shrivathsan
Power saving (in %) of a bulb is directly proportional to square root of its efficiency. By how much % is power saving of bulb-1(efficiency 0.8) greater than power saving of bulb-2 (efficiency 0.2)?

A. 60%
B. 70%
C. 80%
D. 90%
E. 100%
­PSB1 = 0.8 = √x --> x ≈ 0.9
PSB2 = 0.2 = √y --> y ≈ 0.45

Percent Greater Than = x - y / y

0.9 - 0.45 / 0.45 = 0.45 / 0.45 = 1 or 100%


Show more
­
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Power saving of a bulb is directly proportional to square root 29 Jul 2024, 08:12
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Very simple and fast solution

sqrt(0.8)/sqrt(0.2) -1 = (0.8/0.2)^(1/2) -1 = sqrt(4) - 1 = 2 - 1 = 1

Hope it helps!
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Power saving of a bulb is directly proportional to square root 29 Jul 2025, 20:29
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