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
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.