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 2 of 15.
L J Jaswanth said:
2 years ago
WKT,
Average speed over two different speeds in the journey is;
Avg speed= (2XY/X+Y)km/h or M/S.
Where X is the speed during the first half (km/hr or m/s).
And Y is the speed during the second half (km/hr or m/s).
And WKT.
s= d/t and d=s*t.
Here Given
X=21 km/hr.
Y =24 km/hr.
And time over the whole jouneny is 10hrs,
Avg speed = (21*24)/(21+24),
= 22.4 km/hr.
And Total Distance =s*t.
22.4 * 10 = 224 km.
Average speed over two different speeds in the journey is;
Avg speed= (2XY/X+Y)km/h or M/S.
Where X is the speed during the first half (km/hr or m/s).
And Y is the speed during the second half (km/hr or m/s).
And WKT.
s= d/t and d=s*t.
Here Given
X=21 km/hr.
Y =24 km/hr.
And time over the whole jouneny is 10hrs,
Avg speed = (21*24)/(21+24),
= 22.4 km/hr.
And Total Distance =s*t.
22.4 * 10 = 224 km.
(22)
Shivasagar said:
2 years ago
= 2 x 21 * 24/21 + 24 * 10.
= 224.
= 224.
(8)
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)
Akshay said:
2 years ago
2xy/x+y.
= 2*21*24/21+24.
= 1008/45
= 224km.
= 2*21*24/21+24.
= 1008/45
= 224km.
(37)
Akshay said:
2 years ago
Total journey = 10hours.
Journey in 2 parts = 10/2 = 5.
Each journey is = 5hours.
1st journey speed = 21km/hr.
2nd journey speed = 24km/hr.
Total of 1st journey speed = 21 * 5 = 105
Total of 2nd journey speed = 24 * 5 = 120.
So,
Total 1st & 2nd both journey = 105 + 120.
= 225km.
Journey in 2 parts = 10/2 = 5.
Each journey is = 5hours.
1st journey speed = 21km/hr.
2nd journey speed = 24km/hr.
Total of 1st journey speed = 21 * 5 = 105
Total of 2nd journey speed = 24 * 5 = 120.
So,
Total 1st & 2nd both journey = 105 + 120.
= 225km.
(90)
Joy said:
2 years ago
I am not understanding this. Please help me to get this.
(6)
Sivaprakash said:
3 years ago
It may easily be by using averages for 10 hrs- (5*21)+(24*5) = 22.5.
And D = S*T.
22.5 * 10 = 225km
And D = S*T.
22.5 * 10 = 225km
(30)
Bhavin said:
3 years ago
x/21 + x/24 = 20.
24x + 21x = 20* 21 *24,
45x = 10,080,
x =10,080/45.
Ans x = 224.
24x + 21x = 20* 21 *24,
45x = 10,080,
x =10,080/45.
Ans x = 224.
(8)
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)
Aleena said:
3 years ago
Let the time taken for the complete first half = x.
Then the time taken for complete second half will be = 10 - x.
Distance = speed * time.
So,
21x = 24(10-x)
21x = 240-24x
21x + 24x=240
45x = 240
x = 240/45
ie 16/3.
Give the value of x to the first equations.
21x=21 * 16/3.
We get 112.
24(10-x) = 24*(10-16/3).
We get 112.
Just add them both to get the total distance.
ie 224.
Then the time taken for complete second half will be = 10 - x.
Distance = speed * time.
So,
21x = 24(10-x)
21x = 240-24x
21x + 24x=240
45x = 240
x = 240/45
ie 16/3.
Give the value of x to the first equations.
21x=21 * 16/3.
We get 112.
24(10-x) = 24*(10-16/3).
We get 112.
Just add them both to get the total distance.
ie 224.
(7)
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