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 11 of 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).
GHUHI said:
1 decade ago
5*21 = 105 KM.
5*24(KM/HR) = 120 KM.
SO TOTAL DISTANCE TRAVEL.
105+120 = 225.
5*24(KM/HR) = 120 KM.
SO TOTAL DISTANCE TRAVEL.
105+120 = 225.
Sri said:
1 decade ago
USE FORMULA :
Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then,
The average speed during the whole journey is,
= 2(X)(Y)/(X)+(Y).
= 2(21)(24)/21+24.
= 1008/45.
= 22.4KM (AVERAGE SPEED).
NOW WE KNOW THE SPEED, SO SPEED = DISTANCE/TIME.
22.4 = DISTANCE/10 (MULTIPLYING 22.4 * 10 WE GET 224)
224 KMS.
Suppose a man covers a certain distance at x km/hr and an equal distance at y km/hr. Then,
The average speed during the whole journey is,
= 2(X)(Y)/(X)+(Y).
= 2(21)(24)/21+24.
= 1008/45.
= 22.4KM (AVERAGE SPEED).
NOW WE KNOW THE SPEED, SO SPEED = DISTANCE/TIME.
22.4 = DISTANCE/10 (MULTIPLYING 22.4 * 10 WE GET 224)
224 KMS.
Mohit said:
1 decade ago
Can't we solve like this:
21*5=105 and 24*5=5 which equal to 225 instead of 224 why?
21*5=105 and 24*5=5 which equal to 225 instead of 224 why?
Pavan V D said:
1 decade ago
(1/2)x/21+(1/2)x/24 = 10.
x/21+x/24 = 20.
Take LCM,
45x/504 = 20.
x/11.2 = 20.
x = 224.0km.
x/21+x/24 = 20.
Take LCM,
45x/504 = 20.
x/11.2 = 20.
x = 224.0km.
Chandan pal said:
1 decade ago
Avg speed: 2xy/x+y.
Avg speed: 2*21*24/21+24 = 112/5.
Distance = (112/5)*10 = 224.
Avg speed: 2*21*24/21+24 = 112/5.
Distance = (112/5)*10 = 224.
Leelakrishna said:
1 decade ago
2/v = (1/v1)+(1/v2) find v then d = v*t.
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.
Manhar said:
1 decade ago
Hi @Vikash.
Let the total distance = X (becoz we don't know the total distance or journey).
So, 1st half means X/2, 2nd half means also X/2.
That's why we can multiplied with(1/2) in first step.
Let the total distance = X (becoz we don't know the total distance or journey).
So, 1st half means X/2, 2nd half means also X/2.
That's why we can multiplied with(1/2) in first step.
S.vikash said:
1 decade ago
How you multiplied with (1/2) in first step?
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