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If 20% of certain quantity of work is done by A and the rest by B,
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18 May 2016, 08:42
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If 20% of certain quantity of work is done by A and the rest 80% by B, the work is completed in 20 days. If 80% of the work is done by A and the remaining 20% by B, then the work is completed in 30 days. How many days are required to complete the work , if A and B work together. A. 11 1/9 B. 10 1/9 C. 12 D. 15 Source: TIME material.
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Re: If 20% of certain quantity of work is done by A and the rest by B,
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18 May 2016, 09:44
Mohammed22Abrar wrote: If 20% of certain quantity of work is done by A and the rest 80% by B, the work is completed in 20 days. If 80% of the work is done by A and the remaining 20% by B, then the work is completed in 30 days. How many days are required to complete the work , if A and B work together.
A. 11 1/9 B. 10 1/9 C. 12 D. 15
Source: TIME material. Use algebra: 0.2/A + 0.8/B = 20 1/A + 4/B = 100 0.8/A + 0.2/B = 30 4/A+ 1/B = 150 15/B = 250 B = 3/50 work per day A = 3/100 work per day Combined rate = 3/40 + 3/100 = 9/100 Time taken when working together = 100/9 = 11(1/9) days Answer (A) It is not a GMAT type question. For GMAT, it's best to stick to GMAT material.
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Re: If 20% of certain quantity of work is done by A and the rest by B,
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18 May 2016, 10:40
Hello Karishma
Can you please explain how you get this : "0.2/A + 0.8/B = 20" ?
Thanks,
Alex



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Re: If 20% of certain quantity of work is done by A and the rest by B,
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18 May 2016, 21:41
Alex75PAris wrote: Hello Karishma
Can you please explain how you get this : "0.2/A + 0.8/B = 20" ?
Thanks,
Alex Using the formula: Work = Rate * Time Time = Work/Rate Assume A's rate of work is A. Assume B's rate of work is B. A does 20% of the work. So if work is 1, A did .2 of the work. Days for which A worked + Days for which B worked = Total Days (since they work successively) Work of A/Rate of A + Work of B/Rate of B = Total Days .2/A + .8/B = 20
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Re: If 20% of certain quantity of work is done by A and the rest by B,
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20 May 2016, 15:53
Thank you ! it's clear now



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Re: If 20% of certain quantity of work is done by A and the rest by B,
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05 Jul 2016, 16:47
Would anyone be willing to explain why my method didn't work, and why I got a wrong answer?
Eq #1: 0.8 = B *20 Eq #3: 0.8 = A* 30
Solve Eq #1: B = 1/25 = 3/75 using 75 as a common denominator Solve Eq #2: A = 2/75
Combined rate is 5/75. At a rate of 5/75 they will finish in 75/5 = 15 days.
How come this isn't correct?



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Re: If 20% of certain quantity of work is done by A and the rest by B,
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26 Apr 2019, 11:06
Because A & B are not working simultaneously in given situations. So assuming that B took 20 days to finish 80% of the work is wrong because B would have worked lesser number of days than that and same is true with A. You can assume it like B started the work, left it at some point and immediately A took over. pourts wrote: Would anyone be willing to explain why my method didn't work, and why I got a wrong answer?
Eq #1: 0.8 = B *20 Eq #3: 0.8 = A* 30
Solve Eq #1: B = 1/25 = 3/75 using 75 as a common denominator Solve Eq #2: A = 2/75
Combined rate is 5/75. At a rate of 5/75 they will finish in 75/5 = 15 days.
How come this isn't correct?



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Re: If 20% of certain quantity of work is done by A and the rest by B,
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09 Nov 2019, 08:08
Mohammed22Abrar wrote: If 20% of certain quantity of work is done by A and the rest 80% by B, the work is completed in 20 days. If 80% of the work is done by A and the remaining 20% by B, then the work is completed in 30 days. How many days are required to complete the work , if A and B work together.
A. 11 1/9 B. 10 1/9 C. 12 D. 15 rate•time=work 1/5/a+4/5/b=20…1/5a+4/5b=20…b+4a/25ab=20 4/5/a+1/5/b=30…4/5a+1/5b=30…4b+a/25ab=30 4b+a/30=b+4a/20…80b+20a=30b+120a…b=2a 1/5a+4/5b=20…1/5a+4/5(2a)=20…a=3/100 t=1/a+b…t=1/a+2a…t=1/3a…t=1/3(3/100) t=11+1/9 Ans (A)



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If 20% of certain quantity of work is done by A and the rest by B,
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14 Nov 2019, 11:59
VeritasKarishma wrote: Mohammed22Abrar wrote: If 20% of certain quantity of work is done by A and the rest 80% by B, the work is completed in 20 days. If 80% of the work is done by A and the remaining 20% by B, then the work is completed in 30 days. How many days are required to complete the work , if A and B work together.
Hi Karishma, I think in the last step, it should be 3/50 + 3/100 instead of 3/40+3/100. Please check. A. 11 1/9 B. 10 1/9 C. 12 D. 15
Source: TIME material. Use algebra: 0.2/A + 0.8/B = 20 1/A + 4/B = 100 0.8/A + 0.2/B = 30 4/A+ 1/B = 150 15/B = 250 B = 3/50 work per day A = 3/100 work per day Combined rate = 3/40 + 3/100 = 9/100 Time taken when working together = 100/9 = 11(1/9) days Answer (A) It is not a GMAT type question. For GMAT, it's best to stick to GMAT material. Hi Karishma, I think it should be 3/50+3/100 instead of 3/40+3/100. Please check.



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Re: If 20% of certain quantity of work is done by A and the rest by B,
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30 Nov 2019, 22:09
Could you tell me where I am wrong.
I wrote equations like this.
1/5a + 4/5b = 1/20 4/5a + 1/5b = 1/30
I add up both equations and got 1/a + 1/b = 50/600
Here I got A and B did the job in 12 days.
How I did it wrong!




Re: If 20% of certain quantity of work is done by A and the rest by B,
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30 Nov 2019, 22:09






