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# The electricity bill of an office varies directly with the usage of th

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Senior Manager
Joined: 29 Nov 2018
Posts: 280
Concentration: Marketing, Strategy
The electricity bill of an office varies directly with the usage of th  [#permalink]

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18 Feb 2019, 09:56
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59% (02:41) correct 41% (02:23) wrong based on 27 sessions

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The electricity bill of an office varies directly with the usage of the air conditioners. If 8 air conditioners of 1 ton each are used for 8 hrs every day, the monthly bill is 5000. What will the approximate bill amount be, if 12 air conditioners of 1.5 tons each are used for 10 hrs every day?

1. 8000
2. 9000
3. 10000
4. 12000
5. 14000
Intern
Joined: 17 May 2018
Posts: 48
Re: The electricity bill of an office varies directly with the usage of th  [#permalink]

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18 Feb 2019, 10:34
1
First cenario: we're using 8 tons of AC for 8 hours, that's 64 tons-hour for \$5k.
Second cenario: we're using 12*1.5 tons of AC for 10 hours, that's 180 tons-hour. This is almost 3 times our previous usage, which means the cost must be almost 3 times more.
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Intern
Joined: 05 Nov 2017
Posts: 5
Re: The electricity bill of an office varies directly with the usage of th  [#permalink]

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18 Feb 2019, 18:32
8 AC's * 1 ton / day * 8 hrs / Day = 64 tons of AC to rack up a \$5,000 bill

12 AC's * 1.5 ton / day * 10 hrs / Day = 180 tons of AC to rack up a \$X bill.

180/64 is roughly 3x the \$5,000 bill, thus leading us to 14,000.

E.
Intern
Joined: 11 May 2018
Posts: 24
Location: India
Re: The electricity bill of an office varies directly with the usage of th  [#permalink]

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23 Feb 2019, 04:32
let x be the bill amount for 12 AC, 1.5 tons, 10 hrs

x = 5000* 12/8 * 1.5/1* 10/8 = 14062.

approach is similar to rate-work problem. we need to multiply initial cost with the ratios.
for increase in no of ACs, bill will go up --> ratio should be >1 --> 12/8
for increase in tons of ACs, bill will go up --> ratio should be >1 --> 1.5/1
for increase in number of hrs, bill will go up --> ratio should be >1 --> 10/8
Re: The electricity bill of an office varies directly with the usage of th   [#permalink] 23 Feb 2019, 04:32
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