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:
144 comments Page 2 of 15.
Himanshu said:
1 year ago
Let the Distance = 2x.
So, By Formula T = D/S.
The distance covered by each = x.
10 = x/21+x/24,
5040 = 45x,
X = 122.
So Distance =2x,
= 2x122,
=224 Km.
So, By Formula T = D/S.
The distance covered by each = x.
10 = x/21+x/24,
5040 = 45x,
X = 122.
So Distance =2x,
= 2x122,
=224 Km.
(23)
L J Jaswanth said:
3 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)
Francis K Joseph said:
2 years ago
Let's take a formula = 2XY/X + Y.
Here, X=21 and Y= 24.
so, the formula is = 2 * 21 * 24/21 + 24,
=1008/45.
Here, your Answer = 22.4 * 10 = 224.
Here, X=21 and Y= 24.
so, the formula is = 2 * 21 * 24/21 + 24,
=1008/45.
Here, your Answer = 22.4 * 10 = 224.
(22)
Ravinder Choudhary said:
2 years ago
X/21 + X/24 = 10,
15X/168 = 10,
X = 112,
2X = 224.
15X/168 = 10,
X = 112,
2X = 224.
(19)
Sathya said:
3 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)
Bhavin said:
4 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)
Shivasagar said:
3 years ago
= 2 x 21 * 24/21 + 24 * 10.
= 224.
= 224.
(8)
Aleena said:
4 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)
Dish said:
4 months ago
Why can't the answer be calculated like average speed?
We sum up the speeds of 21 and 24, divide by 2, and use that speed in the formula.
Multiply 10 hours by 22.5 kmph and get 225 km!
@All.
Here I got a different answer. I am not getting it clearly. So, can anyone clarify this to me?
We sum up the speeds of 21 and 24, divide by 2, and use that speed in the formula.
Multiply 10 hours by 22.5 kmph and get 225 km!
@All.
Here I got a different answer. I am not getting it clearly. So, can anyone clarify this to me?
(7)
Shubham said:
4 years ago
@Naveen.
LCM of 21 and 24 is 168,
168/21 = 7,
168/24 = 8.
But the simple way to solve this question is;
Avrg speed = 2xy/x+y,
2 * 21 * 24/ 21+24,
1008/45 = 22.4.
Distance = speed * time,
= 22.4 *10 =224 km/h.
LCM of 21 and 24 is 168,
168/21 = 7,
168/24 = 8.
But the simple way to solve this question is;
Avrg speed = 2xy/x+y,
2 * 21 * 24/ 21+24,
1008/45 = 22.4.
Distance = speed * time,
= 22.4 *10 =224 km/h.
(6)
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