Hi
nick1816 and
Bunuel,
I solved it using the tedious approach. But I have a few concerns regarding pt II and pt III.
Let distance till lake = L.
2.5 <= L <= 3 => 5 <= 2L <= 6 ----- this is the distance traveled by Rob in time 55 <= T <= 65 mins.
Distance covered by Tim: 10 <= 2L+5 <= 11.
Time taken by Tim: 120 mins
I. The walking speed of Timothy was greater than that of Robert
We need to compare the min speed of Timothy with the max speed of Robert.
Min T = 10/120 = 1/12
Max R = 6/55 ~ 1/9 which is greater than Min T.
So pt 1 is false.
II. Robert’s walking speed was close to 3 kilometers per hour
Min speed of R = 5/(13/12) ~ 5 kmph, greater than 3 kmph. Not close.
But this is very ambiguous because the degree of closeness can't be defined here. For ex, if we compare 3 to 15 and 3 to 5, then 3 to 5 is close.
III. Had Robert covered 5 more meters every 18 seconds, his walking speed would have been greater than Timothy’s
5mt/18s = 1kph.
Let's compare Robert's minimum speed with Timothy's maximum speed.
R's min speed = (5+(13/12))/65 = 73/(12*65) ~ 1/11
T's max speed = 11/120 ~ 1/12 which is less than R's speed of 1/11. So, pt 3 is always true.
However, the exact value of R(min) = 0.093 and T(max) = 0.091. When the exact values are this close, rounding even a single unit can in turn return the wrong result. But calculating these values are not possible in the time frame of GMAT.
Kindly suggest what is the best suited approach to such questions.
Regards
Lipun