Aptitude - Time and Distance - Discussion
Discussion Forum : Time and Distance - General Questions (Q.No. 7)
7.
A man complete a journey in 10 hours. He travels first half of the journey at the rate of 21 km/hr and second half at the rate of 24 km/hr. Find the total journey in km.
Answer: Option
Explanation:
| (1/2)x | + | (1/2)x | = 10 |
| 21 | 24 |
 |
x | + | x | = 20 |
| 21 | 24 |
15x = 168 x 20
| x = |
 |
168 x 20 |  |
= 224 km. |
| 15 |
Discussion:
141 comments Page 8 of 15.
Neelima said:
1 decade ago
L.C.M of 21, 24 with 3 ans is =3, 7, 8 = multiply you get 168
x/21 + x/24 = 7x + 8x/168 = 20
15x = 20 * 168
x = (20 * 168) / 15
x/21 + x/24 = 7x + 8x/168 = 20
15x = 20 * 168
x = (20 * 168) / 15
Ketaki said:
1 decade ago
If any object does journey in 'T' hours the 1st half at a km/hr and 2nd half at b km/hr the total distance is :(2*T*a*b)/(a+b).
Aman said:
5 years ago
average speed = 2xy/x+y.
So, 2*21*24/21+24.
2*21*24/45,
112/5=22.4.
Distance = time * speed.
= 10*22.4 =>224 kms.
So, 2*21*24/21+24.
2*21*24/45,
112/5=22.4.
Distance = time * speed.
= 10*22.4 =>224 kms.
(1)
Sneha said:
10 years ago
I ll tell you people the easiest method.
Average speed = 2xy/(x+y) = 22.4.
Time is given 10 hrs.
So 10x22.4 = 224.
Average speed = 2xy/(x+y) = 22.4.
Time is given 10 hrs.
So 10x22.4 = 224.
Alpesh said:
7 years ago
Why don't you take average speed and multiply with the time?
I get average speed 72 and distance is 720. Am I right?
I get average speed 72 and distance is 720. Am I right?
Vissu said:
1 decade ago
Its simple. Average of two speeds 21 kmphr and 24 kmphr is 1008/45.
Now dist = speed x time = (1008/45) x 10 = 224.
Now dist = speed x time = (1008/45) x 10 = 224.
Asit said:
1 decade ago
We know that the avg speed =2xy/x+y
so 2*21*24/21+24=112/5 km/hr
then distance=speed*time
=>112/5 * 10=224 km.
so 2*21*24/21+24=112/5 km/hr
then distance=speed*time
=>112/5 * 10=224 km.
Rakshii said:
3 years ago
First, half of the journey is nothing but 5hr,
So, distance = speed * time.
21*5 = 105.
24*5 = 120.
Total= 225km
So, distance = speed * time.
21*5 = 105.
24*5 = 120.
Total= 225km
(70)
Manoj said:
8 years ago
Avg.of two speeds = (24+21)/2 = 22.5km/hr.
Time = 10 hr.
Distance = speed*time = 22.5*10 = 225km/hr ~ 224km/hr.
Time = 10 hr.
Distance = speed*time = 22.5*10 = 225km/hr ~ 224km/hr.
Sakpal poonam said:
1 decade ago
Total average speed = (2*24*21)/(21+24).
Speed = 1008/45.
Distance = speed/time.
= (1008/45)/10.
= 224 km.
Speed = 1008/45.
Distance = speed/time.
= (1008/45)/10.
= 224 km.
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