Instructions

Directions for the following two questions: 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. It reduces or increases the speed of plane by 50 km per hour depending on direction of flight.

Solution

Let the speed of the plane be p Kmph.

So the speed of plane from A to B will be 'p+50' and the speed from B to A will be 'p-50'.

We notice that the plane goes from B to A stays there for 1 hr and again come back to B with total time duration 12 hrs.

So we have $$\frac{3000}{p-50} + 1 + \frac{3000}{p+50} = 12$$.

We can clearly see that speed of the plane is 550 which satisfies the above equation.

So for the journey of B to A, the plane takes $$\frac{3000}{550-50} = 6$$ hrs.

So time at B when plane reaches at A is 2 pm .

Hence the time difference between A and B is 1 hr.

Alternatively,

Let speed of flight be s,

Since A is to the east of B, A is ahead of be in time

Let A be ahead of B in time by a hours

Departure from A = 4PM, Arrival at B = 8PM

Travel time = 8 - 4 +a = 4 + a

Since City B is behind city A by 'a' hours, the actual travel time is 'a' hours more than the difference of local times.

Similarly when one travels from B to A, since B is ahead of A by 'a' hrs, actual travel time is 'a' hours less than total

i.e. B->A Travel time = (3PM - 8AM) - a = 7 -a

Total distance travelled = Speed $$\times$$ Time taken ....(1)

From A to B, the wind is favourable / in same direction as flight

Hence from (1), we have

A->B >>> $$3000 = (s+50)(4+a) => 3000(7-a) = (s+50)(4+a)(7-a)$$ ...(2)

B->A >>> $$3000 = (s-50)(7-a) => 3000(4+a) = (s-50)(7-a)(4+a)$$ ...(3)

(2) - (3) => $$3000(3-2a) = 100(7-a)(4+a) => a^2-63a+62=0 => a=1/62$$

Hence the time difference between A and B is 1 hr.

Create a FREE account and get:

- All Quant CAT complete Formulas and shortcuts PDF
**35+**CAT previous papers with video solutions PDF- 5000+ Topic-wise Previous year CAT Solved Questions for Free

CAT Probability, Combinatorics QuestionsCAT Remainders QuestionsCAT Venn Diagrams QuestionsCAT Inequalities QuestionsCAT Time Speed Distance Questions

CAT Quant Based DI QuestionsCAT DI Miscellaneous QuestionsCAT Quant Based LR QuestionsCAT Arrangement QuestionsCAT DI with connected data sets Questions