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:
143 comments Page 4 of 15.
Diana said:
5 years ago
First half of the journey, means the first half of the distance to be travelled. Not, the first half of the time required to reach your destination! That's how it is 224 instead of 225.
(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)
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)
Santu said:
5 years ago
How come 15? Please explain.
(1)
Sri Naveen said:
4 years ago
@Amit Kr. Soni.
Anyone please explain to me that how 7x&8x came there?
Anyone please explain to me that how 7x&8x came there?
(1)
Shadab said:
2 decades ago
How this 15x arrives?
Manabendra said:
2 decades ago
Sir, would you please explaine me the 1st line of your explanation?
Rati said:
2 decades ago
I am not getting the answer. If we use another method by finding avg. of speed
ie. 21+24=45/2=22.5x10=225
& even we calculate separately
ie. 5x21 = 105
5x24 = 120
Then 105+120=225
I am confused pls explain
ie. 21+24=45/2=22.5x10=225
& even we calculate separately
ie. 5x21 = 105
5x24 = 120
Then 105+120=225
I am confused pls explain
Amit Kr. Soni said:
2 decades ago
Rati, your method for getting average of speed is wrong,
Because formla of average of speed is = Total distance traveled/Total time taken.
Now let me solve the problem.
Let the total distance = X
& 1st half means X/2
2nd half means also X/2
Again time 4 1st half= X/2*21 =X/42, time 4 2nd half = X/48
According to question: X/42 X/48 = 10hrs.
or, 7x+8x/336=10
or, 15x=3360
So X = 224 Answer.
Because formla of average of speed is = Total distance traveled/Total time taken.
Now let me solve the problem.
Let the total distance = X
& 1st half means X/2
2nd half means also X/2
Again time 4 1st half= X/2*21 =X/42, time 4 2nd half = X/48
According to question: X/42 X/48 = 10hrs.
or, 7x+8x/336=10
or, 15x=3360
So X = 224 Answer.
Sarika datir said:
2 decades ago
We can calculate it by using formula of avg speed also.
x=21,y=24
Formula of avg spped=2xy/x+y
=2(21*24)/21+24
=1008/45=22.4KM/hr
avg spped=22.4km/hr
distance=Speed* time=22.4*10=224km
x=21,y=24
Formula of avg spped=2xy/x+y
=2(21*24)/21+24
=1008/45=22.4KM/hr
avg spped=22.4km/hr
distance=Speed* time=22.4*10=224km
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