Vyshak wrote:
Total distance = 80
Distance = Speed * Time
Walking speed = s1 = 8
Walking time = t1
Bike speed = s2 = 16
Time traveled in bike = t2
d1 + d2 = 80
s1t1 + s2t2 = 80
8*t1 + 16*t2 = 80
t1 + 2*t2 = 10 ----- (1)
Given: t1 + t2 = 8 ----- (2)
(1) - (2) --> t2 = 2 and t1 = 8 - 2 = 6
Walking distance = s1*t1 = 8*6 = 48
Answer: C
Hi Vyshak,
you are correct, BUT
Alligation or Weighted average method..is the fastest method in such Qs
It enables us to find the ratio in which two or more ingredients at the given price/%/weight must be mixed to produce a mixture of a desired price/%/weight.Lets manipulate this Q to fit into weighted average method--
here the walking speed= 8mph, so time he would take cover 80miles= 80/8=10 hr
similarly the biking speed= 16mph, so time he would take cover 80miles= 80/16=5 hr
But the average has to be 8hrs, so the ratio of dist by walking = \(\frac{(Avg-biking time)}{(walking time-biking time)}= \frac{(8-5)}{(10-5)}= \frac{3}{5}\)
so the distance travelled = 3/5 th of total = 3/5 *80 = 48
Thanks for the solution, I was able to solve it using traditional method and was able to follow your weighted average method.
Can you pls explain that instead of using Average time taken for weighted average method, why can't we use directly the respective speeds given ( 8 mph, 16 mph etc).