An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average

Question

An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average speed of 500 mph. The cities are 2200 miles apart. On a certain day while returning from N to M, the aircraft faced extreme bad weather, and therefore had to make an emergency landing in city P, which is 2000 miles away from city N and 600 miles from city M. Once the weather improved, it started from P and moved to M at normal speed. Find the average speed of the aircraft in the whole journey, starting from M and coming back to the same place, if due to bad weather its speed deceases by 100 mph.

A. 425.5 mph
B. 452.8 mph
C. 465.6 mph
D. 470 mph
E. 475.2 mph

OA B

Source: e-GMAT

ravinikhil · Answer

m -> n 500 mph 2000 m 4.4 hrs n-> p 2000 m 400 mph 5 hrs p->m 600 m 500 mph 1.2 hr total - 4800 / 10.6 avg speed 452.8 mph

swerve · Answer

BTGmoderatorDC wrote: ↑Wed Sep 09, 2020 6:17 pm An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average speed of 500 mph. The cities are 2200 miles apart. On a certain day while returning from N to M, the aircraft faced extreme bad weather, and therefore had to make an emergency landing in city P, which is 2000 miles away from city N and 600 miles from city M. Once the weather improved, it started from P and moved to M at normal speed. Find the average speed of the aircraft in the whole journey, starting from M and coming back to the same place, if due to bad weather its speed deceases by 100 mph. A. 425.5 mph B. 452.8 mph C. 465.6 mph D. 470 mph E. 475.2 mph OA B Source: e-GMAT Average Speed $= \dfrac{\text{Distance}}{\text{Time}}$ Aircraft cruises at average speed of $500$mph when weather was fine while moving from $M \rightarrow N$ and later from $P \rightarrow M$. $T(a) = \dfrac{2200 + 600}{500} = 5.6$hrs Its speed reduced by $100$mph while moving in bad weather i.e. from $N \rightarrow P$ $T(b) = \dfrac{2000}{400} = 5$hrs Average Speed $= \dfrac{2200 + 2000 + 600}{5 + 5.6} = 452.83$mph

Scott@TargetTestPrep · Answer

BTGmoderatorDC wrote: ↑Wed Sep 09, 2020 6:17 pm An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average speed of 500 mph. The cities are 2200 miles apart. On a certain day while returning from N to M, the aircraft faced extreme bad weather, and therefore had to make an emergency landing in city P, which is 2000 miles away from city N and 600 miles from city M. Once the weather improved, it started from P and moved to M at normal speed. Find the average speed of the aircraft in the whole journey, starting from M and coming back to the same place, if due to bad weather its speed deceases by 100 mph. A. 425.5 mph B. 452.8 mph C. 465.6 mph D. 470 mph E. 475.2 mph OA B Solution: The plane traveled a total of 2200 + 2000 + 600 = 4800 miles. It took 2200/500 = 4.4 hours to travel from M to N. It took 2000/400 = 5 hours to travel from N to P. It took 600/500 = 1.2 hours to travel from P to M. We use the formula: average speed = total distance / total time. Therefore, the average speed for the round trip was 4800 / (4.4 + 5 + 1.2) = 4800/10.6 ≈ 452.8 mph. Answer: B

Choose how you want to prepare

Get Ready for GMAT Test Day Faster with Live Online Classes

Target Test Prep EA OnDemand

Target Test Prep GMAT OnDemand

An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average

Re: An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average

Re: An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average

GMAT/MBA Expert

Re: An aircraft makes a to-and-fro journey every day between the capital cities of two countries M and N, at an average

Chicago Booth

GMAT Course Reviews

Admissions Consulting Reviews

FREE GMAT PREP RESOURCES

GMAT PREP DEAL TRACKER