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 5 of 15.
Neelima said:
2 decades ago
L.C.M of 21, 24 with 3 ans is =3, 7, 8 = multiply you get 168
x/21 + x/24 = 7x + 8x/168 = 20
15x = 20 * 168
x = (20 * 168) / 15
x/21 + x/24 = 7x + 8x/168 = 20
15x = 20 * 168
x = (20 * 168) / 15
Abhishek said:
1 decade ago
(x/21)+(x/24)=20;
taking LCM,we get-
(45x/504)=20;
and 45/504=15/168;
so 15x=168*20;
x=224;
taking LCM,we get-
(45x/504)=20;
and 45/504=15/168;
so 15x=168*20;
x=224;
Sidhila said:
1 decade ago
@abhishek
How did you get 20?
How did you get 20?
Asit said:
1 decade ago
We know that the avg speed =2xy/x+y
so 2*21*24/21+24=112/5 km/hr
then distance=speed*time
=>112/5 * 10=224 km.
so 2*21*24/21+24=112/5 km/hr
then distance=speed*time
=>112/5 * 10=224 km.
Suchita said:
1 decade ago
These are so much difficult.
Somebody have simple and easy way?
Somebody have simple and easy way?
Jinto said:
1 decade ago
@suchitha
First calculate average speed of 21 and 24 using the formula 2xy/x+y then multiply it with 10 then we will get the answer distance = speed*time easy method.
First calculate average speed of 21 and 24 using the formula 2xy/x+y then multiply it with 10 then we will get the answer distance = speed*time easy method.
Hemansu said:
1 decade ago
Can anyone explain me how did we get 20minutes.
Atul said:
1 decade ago
Question first line: man completes journey in 10 hrs.
In second line: he travels 1/2 of total distance (x) not the time at the rate of 21 km/hr
and 1/2 distance (x) not time at the rate of 25 km/hr.
TIME =DISTANCE/SPEED :1:((DISTANCE=1/2x)/(SPEED=21)for first half
:2:((DISTANCE=1/2x)/(SPEED=25)for second half
TOTAL TIME 10hrs =:1:+:2: =((1/2)x/21)+((1/2)x/24)
In second line: he travels 1/2 of total distance (x) not the time at the rate of 21 km/hr
and 1/2 distance (x) not time at the rate of 25 km/hr.
TIME =DISTANCE/SPEED :1:((DISTANCE=1/2x)/(SPEED=21)for first half
:2:((DISTANCE=1/2x)/(SPEED=25)for second half
TOTAL TIME 10hrs =:1:+:2: =((1/2)x/21)+((1/2)x/24)
Anu said:
1 decade ago
Thanks sarika.
Abhinav said:
1 decade ago
The best way to choose the answer.
Check the option and find the multiple of 21 (divisible by 7) and.
(b) is right because it's a divisble by 7 and also multiple of 21.
Check the option and find the multiple of 21 (divisible by 7) and.
(b) is right because it's a divisble by 7 and also multiple of 21.
Post your comments here:
Quick links
Quantitative Aptitude
Verbal (English)
Reasoning
Programming
Interview
Placement Papers