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# Towns X is 3600 km to the west of Town Y.

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Manager
Joined: 16 Oct 2011
Posts: 66
Location: United States
Schools: Haas EWMBA '23
Towns X is 3600 km to the west of Town Y.  [#permalink]

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10 Aug 2019, 14:13
1
4
00:00

Difficulty:

75% (hard)

Question Stats:

41% (02:36) correct 59% (03:38) wrong based on 22 sessions

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Towns X is 3600 km to the west of Town Y. An Airline operates non-stop flights between X and Y. Its schedule is tabulated as below. The given time is the local time on the same day.

Departure from Town Y at 4.00PM and Arrival at Town X at 7.30 PM
Departure from Town X at 3.00AM and Arrival at Town Y at 1.30 PM

The planes cruise at the same speed in both directions. However, a steady wind blows from Y to X at 75 KMPH. The effective speed of each plane is affected by this.

Find the time difference between X and Y.

A) 2 hrs
B) 2.5 hrs
C) 3 hrs
D) 4.5 hrs
E) 1.5 hrs
DS Forum Moderator
Joined: 19 Oct 2018
Posts: 1853
Location: India
Towns X is 3600 km to the west of Town Y.  [#permalink]

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10 Aug 2019, 15:38
1
Assume there is x hours time difference between town X and town Y, and v is speed of airplane.

For trip from Y to X
$$\frac{3600}{3.5+x}$$=v+75......(1)

For trip from X to Y
$$\frac{3600}{10.5-x}$$=v-75........(2)

subtract equation (2) from (1), we get
$$\frac{3600}{3.5+x}$$- $$\frac{3600}{10.5-x}$$=150

$$\frac{24}{3.5+x}$$- $$\frac{24}{10.5-x}$$=1

Either we can make a quadratic equation and find the roots, or we can check which option satisfies our equation. Later approach is quicker tho.

At x=2.5
$$\frac{24}{3.5+2.5}$$- $$\frac{24}{10.5-2.5}$$=1

$$\frac{24}{6}$$- $$\frac{24}{8}$$=1
4-3=1
1=1

B

pathy wrote:
Towns X is 3600 km to the west of Town Y. An Airline operates non-stop flights between X and Y. Its schedule is tabulated as below. The given time is the local time on the same day.

Departure from Town Y at 4.00PM and Arrival at Town X at 7.30 PM
Departure from Town X at 3.00AM and Arrival at Town Y at 1.30 PM

The planes cruise at the same speed in both directions. However, a steady wind blows from Y to X at 75 KMPH. The effective speed of each plane is affected by this.

Find the time difference between X and Y.

A) 2 hrs
B) 2.5 hrs
C) 3 hrs
D) 4.5 hrs
E) 1.5 hrs
Manager
Joined: 20 Apr 2019
Posts: 112
Re: Towns X is 3600 km to the west of Town Y.  [#permalink]

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20 Aug 2019, 23:54
nick1816 wrote:
Assume there is x hours time difference between town X and town Y, and v is speed of airplane.

For trip from Y to X
$$\frac{3600}{3.5+x}$$=v+75......(1)

For trip from X to Y
$$\frac{3600}{10.5-x}$$=v-75........(2)

subtract equation (2) from (1), we get
$$\frac{3600}{3.5+x}$$- $$\frac{3600}{10.5-x}$$=150

$$\frac{24}{3.5+x}$$- $$\frac{24}{10.5-x}$$=1

Either we can make a quadratic equation and find the roots, or we can check which option satisfies our equation. Later approach is quicker tho.

At x=2.5
$$\frac{24}{3.5+2.5}$$- $$\frac{24}{10.5-2.5}$$=1

$$\frac{24}{6}$$- $$\frac{24}{8}$$=1
4-3=1
1=1

B

pathy wrote:
Towns X is 3600 km to the west of Town Y. An Airline operates non-stop flights between X and Y. Its schedule is tabulated as below. The given time is the local time on the same day.

Departure from Town Y at 4.00PM and Arrival at Town X at 7.30 PM
Departure from Town X at 3.00AM and Arrival at Town Y at 1.30 PM

The planes cruise at the same speed in both directions. However, a steady wind blows from Y to X at 75 KMPH. The effective speed of each plane is affected by this.

Find the time difference between X and Y.

A) 2 hrs
B) 2.5 hrs
C) 3 hrs
D) 4.5 hrs
E) 1.5 hrs

What exactly does the 150 stand for? The difference in speed of the airplanes?
Re: Towns X is 3600 km to the west of Town Y.   [#permalink] 20 Aug 2019, 23:54