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 3 of 15.
John said:
9 years ago
Given,
Total time = 10 hours.
Speed 1(u)= 21 km/hr.
Speed 2 (v)= 24 km/hr.
Distance = ?
We know,
Average speed = 2uv/u + v.
= 2 * 21 * 24/ 21 + 24.
= 22.4 km/hr.
Now,
Distance = Speed * Time.
= 22.4 * 10
= 224 km which is the required answer.
It's as simple as that.
Total time = 10 hours.
Speed 1(u)= 21 km/hr.
Speed 2 (v)= 24 km/hr.
Distance = ?
We know,
Average speed = 2uv/u + v.
= 2 * 21 * 24/ 21 + 24.
= 22.4 km/hr.
Now,
Distance = Speed * Time.
= 22.4 * 10
= 224 km which is the required answer.
It's as simple as that.
Shahbaz Ahmed said:
7 years ago
The easiest method is just take ratio as-
21:24=7:8(speed ratio) & sp is inversely proportion to time so 8:7(time ratio).
Now 8+7=15 portion =10hrs so 1 portion =2/3 hrs so 8 portion =16/3 hrs.
Now, dis=21*(16/3)=112(this is half dis).
So whole dis=112*2=224 km.
21:24=7:8(speed ratio) & sp is inversely proportion to time so 8:7(time ratio).
Now 8+7=15 portion =10hrs so 1 portion =2/3 hrs so 8 portion =16/3 hrs.
Now, dis=21*(16/3)=112(this is half dis).
So whole dis=112*2=224 km.
(1)
Hardik Maheshwari said:
5 years ago
I think the ans should be 225 because in first half mean in 5km he covered distance at a speed of 21kmph.
=21 * 5=105.
And in second half it mean 5km he covered distance at a speed of 24kmph =24 * 5=120.
By adding both distance=105+120=225.
Hence the ans should be 225.
=21 * 5=105.
And in second half it mean 5km he covered distance at a speed of 24kmph =24 * 5=120.
By adding both distance=105+120=225.
Hence the ans should be 225.
(1)
AANI said:
2 years ago
Total journey = 10 hours.
Journey in 2 parts 10/2 = 5
each journey is = 5 hours.
1st journey speed =21 km/hr ;
Total of 1st journey speed = 21 x 5 =105
Total of 2nd journey speed =24 x 5 =120.
Then,
Total 1st and 2nd both journey speed = 105 + 120 = 225 km.
THANKS.
Journey in 2 parts 10/2 = 5
each journey is = 5 hours.
1st journey speed =21 km/hr ;
Total of 1st journey speed = 21 x 5 =105
Total of 2nd journey speed =24 x 5 =120.
Then,
Total 1st and 2nd both journey speed = 105 + 120 = 225 km.
THANKS.
(386)
SAURAV KUMAR said:
6 years ago
We can calculate it by the average formula:
2(21*24)/21+24 = 2(504)/45.
= 1008/45,
= 22.4.
Then the distance travelled in 10hours.
= 22.4 * 10,
= 224.
2(21*24)/21+24 = 2(504)/45.
= 1008/45,
= 22.4.
Then the distance travelled in 10hours.
= 22.4 * 10,
= 224.
Sathya said:
2 years ago
T = 10hrs.
Distance = x
For first half,
when the distance is x/2, speed is 21km/hr.
For the second half
when the distance is x/2, the speed is 24km/hr.
then ,time=distance/speed.
10 = x/2/21+x/2/24;
10 = x/42+x/48,
10 = (48x+42x)/2016,
20160 = 90x,
x = 224km.
Distance = x
For first half,
when the distance is x/2, speed is 21km/hr.
For the second half
when the distance is x/2, the speed is 24km/hr.
then ,time=distance/speed.
10 = x/2/21+x/2/24;
10 = x/42+x/48,
10 = (48x+42x)/2016,
20160 = 90x,
x = 224km.
(18)
Syed said:
1 decade ago
To apply formulae 2uv/(u+v),
where,
s = Distance;
u = First Half velocity which is 21kmph
v = Second Half Velocity which is 24kmph
=>(2*21*24)/(21+24)
=>(1008)/45
=>22.4kmph.
Therefore,average speed = 22.4km/hr
s = vt
s = 22.4km/hr x 10hrs
s=224km.
where,
s = Distance;
u = First Half velocity which is 21kmph
v = Second Half Velocity which is 24kmph
=>(2*21*24)/(21+24)
=>(1008)/45
=>22.4kmph.
Therefore,average speed = 22.4km/hr
s = vt
s = 22.4km/hr x 10hrs
s=224km.
Sudarshan said:
6 years ago
The formula to find avg speed is;
Avg speed= 2(s1)(s2)/(s1+s2).
where s1 and s2 are speeds
On calculating, the avg speed comes out to be 112/5.
Now to find the distance, we have a formula i.e, distance = speed x time.
Distance = (112/5) x 10 = 224km.
Avg speed= 2(s1)(s2)/(s1+s2).
where s1 and s2 are speeds
On calculating, the avg speed comes out to be 112/5.
Now to find the distance, we have a formula i.e, distance = speed x time.
Distance = (112/5) x 10 = 224km.
Vinay said:
10 years ago
First half journey is 21 km/hr and 2 and half is 24 km/hr.
So we can calculate as 21*10 = 210 and divide as half by 2 is 105 same as it as for 24 km 24*10 = 240 and divide as half = 120.
So 120+110 = 225.
Then how is 224? Is this logic is also correct?
So we can calculate as 21*10 = 210 and divide as half by 2 is 105 same as it as for 24 km 24*10 = 240 and divide as half = 120.
So 120+110 = 225.
Then how is 224? Is this logic is also correct?
Dhaval said:
7 years ago
Hear if total distance is X.
And hear fix first 1/2 at fix speed and another half at other fix speed.
So we can assume avg speed so [ speed (1) + speed (2) ] / 2 so we get avg speed for a total this x.
Then for 10 hr final answer is *10 so we get 225.
And hear fix first 1/2 at fix speed and another half at other fix speed.
So we can assume avg speed so [ speed (1) + speed (2) ] / 2 so we get avg speed for a total this x.
Then for 10 hr final answer is *10 so we get 225.
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