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Grass on a lawn grows everyday by a fixed percent of the height on the

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New post 10 Jul 2017, 02:44
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Grass on a lawn grows everyday by a fixed percent of the height on the previous day. However, cows graze and reduce the height of the grass by 1 mm every day. What was the height of the grass on the first day before the cows started grazing? Assume that the cows graze at the end of the day, after which the grass grows in the beginning of the next day.

(1) The grass grows every day by 2 percent of the height on the previous day.
(2) The grass is completely grazed in 3 days.

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New post 10 Jul 2017, 03:37
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Grass on a lawn grows everyday by a fixed percent of the height on the previous day. However, cows graze and reduce the height of the grass by 1 mm every day. What was the height of the grass on the first day before the cows started grazing? Assume that the cows graze at the end of the day, after which the grass grows in the beginning of the next day.

(1) The grass grows every day by 2 percent of the height on the previous day.
(2) The grass is completely grazed in 3 days.
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New post 11 Jul 2017, 06:27
Bunuel wrote:
Grass on a lawn grows everyday by a fixed percent of the height on the previous day. However, cows graze and reduce the height of the grass by 1 mm every day. What was the height of the grass on the first day before the cows started grazing? Assume that the cows graze at the end of the day, after which the grass grows in the beginning of the next day.

(1) The grass grows every day by 2 percent of the height on the previous day.
(2) The grass is completely grazed in 3 days.


stat 1: grass grows every day by 2% .. no info on absolute values,,hence not suff

stat 2: if the grass is grazed at the end of 3 days... on third day the grass will 1mm before grazing....
on third day morning the grass will be some percent of the previous day..by what percent?? no info..not suff

both combined suff
ans C
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New post 15 Jul 2017, 03:50
Bunuel wrote:
Grass on a lawn grows everyday by a fixed percent of the height on the previous day. However, cows graze and reduce the height of the grass by 1 mm every day. What was the height of the grass on the first day before the cows started grazing? Assume that the cows graze at the end of the day, after which the grass grows in the beginning of the next day.

(1) The grass grows every day by 2 percent of the height on the previous day.
(2) The grass is completely grazed in 3 days.


Assume growth everyday is x% and initial height is H

(1) X = 2. But this statement does not say anything about the height on any particular day. NOT SUFFICIENT

(2) H(1+x)^3 - 3(1) =0. NOT SUFFICIENT as no information on H and x provided

(1) + (2) . x = 2. Hence, H(1+2%)^3 - 3(1) =0. Solvable and Sufficient

Hence C
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Re: Grass on a lawn grows everyday by a fixed percent of the height on the  [#permalink]

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New post 09 Aug 2017, 13:35
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Bunuel wrote:
Grass on a lawn grows everyday by a fixed percent of the height on the previous day. However, cows graze and reduce the height of the grass by 1 mm every day. What was the height of the grass on the first day before the cows started grazing? Assume that the cows graze at the end of the day, after which the grass grows in the beginning of the next day.

(1) The grass grows every day by 2 percent of the height on the previous day.
(2) The grass is completely grazed in 3 days.


Let initial height be h
Acc to 1===> then at the end of third day after grazing the height would be H(final) = [[[1.2h -1]*1.2 - 1]*1.2 - 1], but we do not know the final height H(final) so we cannot determine h, insufficient
Acc to 2====> We do not know how much does the percent the height increases daily.

Combined we know H(final) =0 ==> [[[1.2h -1]*1.2 - 1]*1.2 - 1] =0, and we can determine h.....sufficient
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Re: Grass on a lawn grows everyday by a fixed percent of the height on the   [#permalink] 09 Aug 2017, 13:35
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