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 15 of 15.
Muskan said:
5 years ago
AVG.speed=2v1*v2/V1+V2
= 2*21*24/21+24
=22.4km/h.
Distance = speed * time.
=22.4 *10
= 224km.
= 2*21*24/21+24
=22.4km/h.
Distance = speed * time.
=22.4 *10
= 224km.
Charan said:
5 years ago
Let, distance be 'x'
The for the first half, distance = x * 1/2.
For the second half also, distance = x * 1/2.
Then , time = distance/speed.
Therefore, time taken for first half = (x*1/2)/21 = x/42.
Time taken for second half = (x*1/2)24 = x/48.
Therefor total time = x/42 +x/48 and that is given as 10 minutes.
So, x/42+x/48 = 10.
Solving this, you get (48x + 42x) = 48*42*10.
On solving , 90x = 48*42*10.
We get x = 224.
The for the first half, distance = x * 1/2.
For the second half also, distance = x * 1/2.
Then , time = distance/speed.
Therefore, time taken for first half = (x*1/2)/21 = x/42.
Time taken for second half = (x*1/2)24 = x/48.
Therefor total time = x/42 +x/48 and that is given as 10 minutes.
So, x/42+x/48 = 10.
Solving this, you get (48x + 42x) = 48*42*10.
On solving , 90x = 48*42*10.
We get x = 224.
Matheshg said:
4 years ago
@Sarika Datir.
The formula is used when D is constant.
The formula is used when D is constant.
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