tinki wrote:
guy with 1st statement:
here is my calculation:
if it takes 1 hour to walk max 6.4 km
if will take max. 2.5 hours to walk 16 km.
since it says average rate less than 6.4 so time is less than 2.5 but it could be less than 2.
so im getting that A is not suff. whats wrong with my method ?
pls explain
distance=rate*time --> rate and time are
inversely proportional, which means that if you
increase the rate then you'll need
less time to cover the same distance and if you
decrease the rate you'll need
more time to cover the same distance.
So, rate is
less than 6.4 kilometers per hour means that time needed to cover 16 kilometers is
more than 2.5 hours.
Alternate approach:
Did it take Pei more than 2 hours to walk a distance of 10 miles along a certain trail? (1mile = 1.6 Kilometers, rounded to the nearest tenth)Basically the question asks whether the rate was less than 10/2=5 miles per hour:
is rate<5 miles per hour? Because if it is less than 5 miles per hour, then time needed to cover 10 miles would be more than 2 hours.
(1) Pei walked this distance at an average rate of less than 6.4 kilometers per hour --> rate<6.4 kilometers per hour --> 6.4 kilometer = 6.4/1.6 = 4 miles -->
rate<4 miles per hour. Sufficient.
(2) On average, it took Pei more than 9 minutes per Kilometers to walk this distance --> more than 9/60 hours to cover 1 kilometer --> rate<60/9 kilometers per hour (time
more - rate
less) --> 60/9 kilometers = (60/9)/1.6 = ~4.2 miles -->
rate<4.2 miles per hour. Sufficient.
Answer: D.