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A migrating bird flew across a lake at an average speed of 18 meters p

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A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 16 May 2016, 23:12
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A migrating bird flew across a lake at an average speed of 18 meters per second. Was the distance that the bird flew across the lake less than 21 kilometers? (1 kilometer = 1000 meters)

(1) It took the bird less than 20 minutes to fly across the lake.

(2) It took the bird less than 0.4 hour to fly across the lake.

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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 16 May 2016, 23:37
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shasadou wrote:
A migrating bird flew across a lake at an average speed of 18 meters per second. Was the distance that the bird flew across the lake less than 21 kilometers? (1 kilometer = 1000 meters)

(1) It took the bird less than 20 minutes to fly across the lake.

(2) It took the bird less than 0.4 hour to fly across the lake.


Hi,
the moment we are given SPEED and asked for distance, and the choices are in TIME, CHANGE speed and distance in TIME...
At a speed of 18m per sec, the bird will travel 21 kms in 21000/18 secs = 7000/6 seconds or 1167 seconds..
When can we answer the Q-
A) If the time is less than 1167 secs, we can answer the Q as definite YES
B) If the time is greater than 1167 secs, we can answer the Q as definite NO..


lets see the statements



(1) It took the bird less than 20 minutes to fly across the lake.
20 minutes is 1200 secs...
so time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..

(2) It took the bird less than 0.4 hour to fly across the lake.
0.4hour = .4*60 *60 secs = 1440 secs..
we can take same example as in (1)..
again Insuff..

Combined..
the set of examples remain..
time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..
E
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 17 Apr 2017, 20:21
1
shasadou wrote:
A migrating bird flew across a lake at an average speed of 18 meters per second. Was the distance that the bird flew across the lake less than 21 kilometers? (1 kilometer = 1000 meters)

(1) It took the bird less than 20 minutes to fly across the lake.

(2) It took the bird less than 0.4 hour to fly across the lake.



1) Distance covered in 20min = 18x60x20=21600. Therefore, distance is <21600. Insuff.
2) 0.4h = 24min, which allows for a greater distance than 1). Insuff.
1) and 2) Insuff. No new information from using both statements.
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 06 May 2017, 23:04
chetan2u wrote:
shasadou wrote:
A migrating bird flew across a lake at an average speed of 18 meters per second. Was the distance that the bird flew across the lake less than 21 kilometers? (1 kilometer = 1000 meters)

(1) It took the bird less than 20 minutes to fly across the lake.

(2) It took the bird less than 0.4 hour to fly across the lake.


Hi,
the moment we are given SPEED and asked for distance, and the choices are in TIME, CHANGE speed and distance in TIME...
At a speed of 18m per sec, the bird will travel 21 kms in 21000/18 secs = 7000/6 seconds or 1167 seconds..
When can we answer the Q-
A) If the time is less than 1167 secs, we can answer the Q as definite YES
B) If the time is greater than 1167 secs, we can answer the Q as definite NO..


lets see the statements



(1) It took the bird less than 20 minutes to fly across the lake.
20 minutes is 1200 secs...
so time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..

(2) It took the bird less than 0.4 hour to fly across the lake.
0.4hour = .4*60 *60 secs = 1440 secs..
we can take same example as in (1)..
again Insuff..

Combined..
the set of examples remain..
time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..
E



Can you let me know where I went wrong:
I converted Speed into Km/h so its 64.8 Km/h
Now according to first statement t<20 mins i.e less than 1/3 hrs or 0.33 hrs

Now If I calculate the distance taking the max cvalue say 0.32 * 64.8 its 20.7 which is less than 21 hence I marked A.
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 29 Jul 2017, 02:39
ezzo wrote:
chetan2u wrote:
shasadou wrote:
A migrating bird flew across a lake at an average speed of 18 meters per second. Was the distance that the bird flew across the lake less than 21 kilometers? (1 kilometer = 1000 meters)

(1) It took the bird less than 20 minutes to fly across the lake.

(2) It took the bird less than 0.4 hour to fly across the lake.


Hi,
the moment we are given SPEED and asked for distance, and the choices are in TIME, CHANGE speed and distance in TIME...
At a speed of 18m per sec, the bird will travel 21 kms in 21000/18 secs = 7000/6 seconds or 1167 seconds..
When can we answer the Q-
A) If the time is less than 1167 secs, we can answer the Q as definite YES
B) If the time is greater than 1167 secs, we can answer the Q as definite NO..


lets see the statements



(1) It took the bird less than 20 minutes to fly across the lake.
20 minutes is 1200 secs...
so time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..

(2) It took the bird less than 0.4 hour to fly across the lake.
0.4hour = .4*60 *60 secs = 1440 secs..
we can take same example as in (1)..
again Insuff..

Combined..
the set of examples remain..
time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..
E



Can you let me know where I went wrong:
I converted Speed into Km/h so its 64.8 Km/h
Now according to first statement t<20 mins i.e less than 1/3 hrs or 0.33 hrs

Now If I calculate the distance taking the max cvalue say 0.32 * 64.8 its 20.7 which is less than 21 hence I marked A.


Hi ezzo,
Statement 1 says that it took the bird less than 20 minutes(or 0.33hrs) to fly across the lake. The time could be 0.32 hours, or it could be 0.3299 hours.
If the time were 0.32 hours, as you have calculated, the distance is less than 21. However, if the time were 0.3299 hours, the distance is 21.38, which is more than 21km.
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A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 29 Jul 2017, 02:52
1
In these kinds of questions, it is best to first calculate the required information to answer the question, and then compare this information with Statements 1 and 2.
For example, we are given:
s=18 m/s
and we want to find out if total distance is less than 21km.
d>21km or 21,000m

First, convert speed to m/min to make the information comparable to statements 1 and 2.
(18 m/s) (60 s/min) = 18*6 m/min

To calculate the time,
t> 21,000/(18*6) = (7*3*100)/(9*2*3*2) [FACTORING WILL BE EASIER THAN MULTIPLYING THEN EVENTUALLY DIVIDING)
t> 7*25/9
t>175/9
t>19.44

(1) It took the bird less than 20 minutes to fly across the lake.
t could be less than 19.44 or could be more than 19.44. INSUFFICIENT.

(2) It took the bird less than 0.4 hour to fly across the lake.
0.4 hour=24min. Again, t could be less than 19.44 or could be more than 19.44. INSUFFICIENT.


Statement b did not really bring new information as we already know from Statement 1 that t is less than 19.44.
Thus 1&2 INSUFFICIENT.
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 29 Jul 2017, 03:11
ezzo wrote:
chetan2u wrote:
shasadou wrote:
A migrating bird flew across a lake at an average speed of 18 meters per second. Was the distance that the bird flew across the lake less than 21 kilometers? (1 kilometer = 1000 meters)

(1) It took the bird less than 20 minutes to fly across the lake.

(2) It took the bird less than 0.4 hour to fly across the lake.


Hi,
the moment we are given SPEED and asked for distance, and the choices are in TIME, CHANGE speed and distance in TIME...
At a speed of 18m per sec, the bird will travel 21 kms in 21000/18 secs = 7000/6 seconds or 1167 seconds..
When can we answer the Q-
A) If the time is less than 1167 secs, we can answer the Q as definite YES
B) If the time is greater than 1167 secs, we can answer the Q as definite NO..


lets see the statements



(1) It took the bird less than 20 minutes to fly across the lake.
20 minutes is 1200 secs...
so time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..

(2) It took the bird less than 0.4 hour to fly across the lake.
0.4hour = .4*60 *60 secs = 1440 secs..
we can take same example as in (1)..
again Insuff..

Combined..
the set of examples remain..
time can be 1180 , ans is NO
and if time is 1110, ans is YES..
Insuff..
E



Can you let me know where I went wrong:
I converted Speed into Km/h so its 64.8 Km/h
Now according to first statement t<20 mins i.e less than 1/3 hrs or 0.33 hrs

Now If I calculate the distance taking the max cvalue say 0.32 * 64.8 its 20.7 which is less than 21 hence I marked A.


hi dont complicate the calculations by taking decimals..
so t<20min or t<1/3..
thus d<t*speed or d< 64.8*1/3...d<21.6
so d can be 21.5 also and 10 also..
insuff

hope it helps
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 26 Dec 2017, 10:52
Bunuel Do we have a separate question directory for this type of questions? atleast one such question comes in gmat always.
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 26 Dec 2017, 10:58
Prashant10692 wrote:
Bunuel Do we have a separate question directory for this type of questions? atleast one such question comes in gmat always.


16. Distance/Rate Problems



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A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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New post 21 Feb 2018, 14:24
Question: 18t < 21000
=> t < 21000/18 secs?
=> t < 7000/6 secs?
=> t < 7000/360 mins?
=> t < 19.x mins?

Statement 1: It took the bird less than 20 minutes to fly across the lake. => t < 20 mins => not suff
Statement 2: It took the bird less than 0.4 hour to fly across the lake. => t < 24 mins => not suff

combining 1 + 2, t < 20, but still insuff to answer, t < 19.x?=> (E)
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Re: A migrating bird flew across a lake at an average speed of 18 meters p  [#permalink]

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Re: A migrating bird flew across a lake at an average speed of 18 meters p   [#permalink] 25 Apr 2019, 17:22
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