Oct 16 08:00 PM PDT  09:00 PM PDT EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299) Oct 19 07:00 AM PDT  09:00 AM PDT Does GMAT RC seem like an uphill battle? eGMAT is conducting a free webinar to help you learn reading strategies that can enable you to solve 700+ level RC questions with at least 90% accuracy in less than 10 days. Sat., Oct 19th at 7 am PDT Oct 20 07:00 AM PDT  09:00 AM PDT Get personalized insights on how to achieve your Target Quant Score. Oct 22 08:00 PM PDT  09:00 PM PDT On Demand for $79. For a score of 4951 (from current actual score of 40+) AllInOne Standard & 700+ Level Questions (150 questions)
Author 
Message 
TAGS:

Hide Tags

eGMAT Representative
Joined: 04 Jan 2015
Posts: 3074

Two runners, P and Q, competed in a race of 400 m
[#permalink]
Show Tags
Updated on: 13 Aug 2018, 06:06
Question Stats:
52% (03:20) correct 48% (03:05) wrong based on 81 sessions
HideShow timer Statistics
3 common mistakes you must avoid in Distance questions – Practice question 1 Two runners, P and Q, competed in a race of 400 m. P ran at a constant speed of 5 strides in every 2 seconds, covering 10 m in that span. Q started at a constant speed. After running for 1 minute, Q increased its speed by 1 stride per second and finally finished the race at the same time with P. What is Q’s initial speed in kph if Q covered 4 m in every stride? A. 10 kph B. 11.5 kph C. 12.8 kph D. 13.6 kph E. 14.4 kph To solve question 2: Question 2To read the article: 3 common mistakes you must avoid in Distance questions
Official Answer and Stats are available only to registered users. Register/ Login.
_________________



eGMAT Representative
Joined: 04 Jan 2015
Posts: 3074

Re: Two runners, P and Q, competed in a race of 400 m
[#permalink]
Show Tags
Updated on: 20 May 2018, 06:25
Solution Given:• Two runners, P and Q, competed in a race of 400 m • P ran at a constant speed of 5 strides in every 2 seconds, covering 10 m in that span o Hence, in 2 seconds P covered 10 m Or, speed of P = \(\frac{10}{2}\) m/s = 5 m/s • Q started the race at a constant speed • Q covered 4 m in every stride • After running for 1 minute, Q increased its speed by 1 stride per second • Q finished the race, taking the same time as P To find:• The initial speed of Q, in kph Approach and Working: • As the race distance is 400 m and speed of P is 5 m/s, o Time taken by P to finish the race = \(\frac{400}{5}\) secs = 80 seconds • Given that the time taken by P and Q is same, Q also takes 80 seconds to finish the race • Let us assume that in the initial 60 seconds, Q took x strides per second o Therefore, in the last 20 seconds, Q took (x + 1) strides per second • As Q covers 4 m in every stride, the total distance covered by Q = 4 [60x +20(x + 1)] m Or, 4 [60x + 20 (x + 1)] = 400 Or, 60x + 20x + 20 = 100 Or, 80x = 80 Or, x = 1 stride/sec • Given that Q covered 4 m in every stride, the initial speed of Q = 4 m/s = 4 * \(\frac{18}{5}\) kph = \(\frac{72}{5}\) kph = 14.4 kph Hence, the correct answer is option E. Answer: E
_________________



VP
Joined: 07 Dec 2014
Posts: 1222

Re: Two runners, P and Q, competed in a race of 400 m
[#permalink]
Show Tags
16 May 2018, 18:34
EgmatQuantExpert wrote: 3 common mistakes you must avoid in Distance questions – Practice question 1 Two runners, P and Q, competed in a race of 400 m. P ran at a constant speed of 5 strides in every 2 seconds, covering 10 m in that span. Q started at a constant speed. After running for 1 minute, Q increased its speed by 1 stride per second and finally finished the race at the same time with P. What is Q’s initial speed in kph if Q covered 4 m in every stride? A. 10 kph B. 11.5 kph C. 12.8 kph D. 13.6 kph E. 14.4 kph Q's race, like P's, lasts (400/10)*2=80 seconds let x=Q's speed in mps in first minute 60*x+20*(x+4)=400 x=4 mps=14.4 kph E



Director
Joined: 31 Jul 2017
Posts: 512
Location: Malaysia
GPA: 3.95
WE: Consulting (Energy and Utilities)

Re: Two runners, P and Q, competed in a race of 400 m
[#permalink]
Show Tags
18 May 2018, 01:53
EgmatQuantExpert wrote: 3 common mistakes you must avoid in Distance questions – Practice question 1 Two runners, P and Q, competed in a race of 400 m. P ran at a constant speed of 5 strides in every 2 seconds, covering 10 m in that span. Q started at a constant speed. After running for 1 minute, Q increased its speed by 1 stride per second and finally finished the race at the same time with P. What is Q’s initial speed in kph if Q covered 4 m in every stride? A. 10 kph B. 11.5 kph C. 12.8 kph D. 13.6 kph E. 14.4 kph To solve question 2: Question 2To read the article: 3 common mistakes you must avoid in Distance questions Velocity of P = 10/2 = 5m/sec The total time taken by P = 400/5 = 80 sec. Now, out of 80 sec, Q has travelled at a constant speed of a fro 60 sec. Therefore, total distance travelled by Q in 60 Sec = 60a. In the remaining 20 sec... for every 1 Sec the velocity of Q increases by 4m/sec. 400 = 60a + 20a + 80 a = 4m/sec = 14.4kmph
_________________
If my Post helps you in Gaining Knowledge, Help me with KUDOS.. !!



NonHuman User
Joined: 09 Sep 2013
Posts: 13174

Re: Two runners, P and Q, competed in a race of 400 m
[#permalink]
Show Tags
11 Aug 2019, 06:23
Hello from the GMAT Club BumpBot! Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up  doing my job. I think you may find it valuable (esp those replies with Kudos). Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________




Re: Two runners, P and Q, competed in a race of 400 m
[#permalink]
11 Aug 2019, 06:23






