Avila drove from A to B at an average speed of 15 miles per hour, and

Question

Avila drove from A to B at an average speed of 15 miles per hour, and then without stopping traveled from B to C at an average speed of 90 miles per hour. If the distance from A to B is four times the distance from B to C, what was her average speed for the entire journey from A to C, in miles per hour?

A) 18

B) 24

C) 27

D) 30

E) 52.5

Show Answer

Official Answer

A

A) 18

B) 24

C) 27

D) 30

E) 52.5

ElninoEffect · Answer

Let distance from B to C be = x
So distance from A to B = 4x
Total distance = 5x

Avg Speed = 5x/(4x/15) + (x/90) = 5x*90/25x =  18 A

unraveled · Answer

Avila drove from A to B at an average speed of 15 miles per hour, and then without stopping traveled from B to C at an average speed of 90 miles per hour. If the distance from A to B is four times the distance from B to C, what was her average speed for the entire journey from A to C, in miles per hour?

A) 18

B) 24

C) 27

D) 30

E) 52.5

Show Answer

Official Answer

A

A) 18

B) 24

C) 27

D) 30

E) 52.5

Let the distance between A to B is 360 miles. Distance between B to C is 90 miles. Total distance = 450 miles.
T(AB) = 360/15 = 24 hours
T(BC) = 90/90 = 1 hour
Total time = 25 hours

T(avg) = 450/25 = 18 hours

Answer A.

Sabuj40040 · Answer

distance(A,B)=4x, distance(B,C)=x
average speed = total distance/time= (4x+x)/((4x/15)+(x/90))=18

Ritikabest · Answer

Average speed = Total Distance / total time
Total distance = 4D+D = 5D
Total time = 4D/15 + D/90(Time = Distance/Speed formula)
Avg speed= 4D+D/( 4D/15 + D/90)
Solve the equation and you will get D= 18.

Zareensoobuh · Answer

Total distance 5x

4x/15 for ab
X/90 for bc

Total time = 
4x/15+x/90 
= 25x/90 
=5x/18

Avg speed = 5/5x/18=18 kmph

eveismyname · Answer

Since distance A to B is 4 times of distance B to C, we can use any number to represent the distance. Say:
A to B = 360 miles
B to C = 90 miles

total distance travelled is 450 miles
average speed = total distance/total time = 450 divided by (360 miles/rate of 15mph) + (90/ rate of 90 mph) = 450/25
= 18

ANS: A. 18

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Avila drove from A to B at an average speed of 15 miles per hour, and

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