GMAT Question of the Day: Daily via email | Daily via Instagram New to GMAT Club? Watch this Video

 It is currently 18 Feb 2020, 16:28

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Cities A and B are in different time zones. A is located 3000 km east

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 61283
Cities A and B are in different time zones. A is located 3000 km east  [#permalink]

### Show Tags

08 Jan 2020, 01:50
00:00

Difficulty:

55% (hard)

Question Stats:

67% (02:21) correct 33% (02:16) wrong based on 18 sessions

### HideShow timer Statistics

Cities A and B are in different time zones. A is located 3000 km east of B. The table below describes the schedule of an airline operating non-stop flights between A and B. All the times indicated are local and on the same day.

Assume that planes cruise at the same speed in both directions. However, the effective speed is influenced by a steady wind blowing from east to west at 50 km per hour.

What is the plane’s cruising speed in km per hour?

(A) 500
(B) 550
(C) 600
(D) 700
(E) Cannot be determined

Are You Up For the Challenge: 700 Level Questions

_________________
Math Expert
Joined: 02 Sep 2009
Posts: 61283
Re: Cities A and B are in different time zones. A is located 3000 km east  [#permalink]

### Show Tags

08 Jan 2020, 01:50
Bunuel wrote:
Cities A and B are in different time zones. A is located 3000 km east of B. The table below describes the schedule of an airline operating non-stop flights between A and B. All the times indicated are local and on the same day.

Assume that planes cruise at the same speed in both directions. However, the effective speed is influenced by a steady wind blowing from east to west at 50 km per hour.

What is the plane’s cruising speed in km per hour?

(A) 500
(B) 550
(C) 600
(D) 700
(E) Cannot be determined

Are You Up For the Challenge: 700 Level Questions

TWIN QUESTION: https://gmatclub.com/forum/cities-a-and ... 13968.html
_________________
CR Forum Moderator
Joined: 18 May 2019
Posts: 706
Cities A and B are in different time zones. A is located 3000 km east  [#permalink]

### Show Tags

09 Jan 2020, 00:14
Let the time taken for the flight from A to B to Tab and the time from B to A be Tba. Let the speed of the plane be S, and the time difference be Td.
Then from the information provided above, the following equations can be formed.
Tab=7-td --------(1)
Tba=4+td--------(2)
Sab = S+50 -----(3)
Sba = S-50 ------(4)

Since the plane would cover the same distance in a trip from A to B and B to A, Average Speed, Sav, =[(S+50)+(S-50)]/2 = 2S/2 = S.
Average time, Tav, = [(4+td)+(7-td)] = 11/2 = 5.5hrs.

Sav = S = Average distance Between A and B / Average Time = 3000/5.5 = 545 approximately 550km/hr

Manager
Joined: 22 Sep 2018
Posts: 59
Re: Cities A and B are in different time zones. A is located 3000 km east  [#permalink]

### Show Tags

09 Jan 2020, 03:44
given the data ,

let speed of plane is S , t is difference in the time zone.

Time taken while going from B to A = 7hr - t

Time taken while going from A to B = 4hr + t

total time taken during travelling = 7 + 4 = 11

i.e $$\frac{3000}{s-50} + \frac{3000}{s+50} = 11$$ , by plugging in the s = 550kmph exactly.
Intern
Joined: 30 Nov 2019
Posts: 4
GMAT 1: 670 Q46 V36
GMAT 2: 620 Q49 V27
Re: Cities A and B are in different time zones. A is located 3000 km east  [#permalink]

### Show Tags

09 Jan 2020, 05:59
T1 + T2 = 4 + 7 = 11 hours
$$T1=\frac{D1}{V1}=\frac{3000}{(S+50)}$$
$$T2= \frac{D2}{V2}=\frac{3000}{(S-50)}$$
$$\frac{3000}{(S+50)}+\frac{3000}{(S-50)}=11$$

At this stage you can either solve the equation (not recommended) or plug in the numbers. 550 is a perfect fit:

$$\frac{3000}{(500+50)}+\frac{3000}{(550-50)}=5+6=11$$

Re: Cities A and B are in different time zones. A is located 3000 km east   [#permalink] 09 Jan 2020, 05:59
Display posts from previous: Sort by