Aptitude - Time and Distance - Discussion

@All.

Thanks, you all expressed clearly.

Please solve this.

While covering a distance of 60 km, A takes 4 hours more than B. If A doubles its speed, A took 2 hours less than B. Find the walking speed using a simultaneous equation or quadratic equation.

Given;

14kmph at 20 km MORE i.e extra speed.
So we can write it as 4 kmph -20.,
Each km 20÷4 = 5.
Hence 10 * 5 = 50.

Let actual distance x km.
Actual speed =10 kmph T1 = ?

Man walk 20 km more,
Distance = x + 20.
Speed = 14 kmph T2 = ?

Now T1 = T2.
D1/S1 = D2/S2.
x/10 = x + 20/14 after solving x (actual distance) = 50 km answer.

@Gowtham, @Ilesh.

Both are explained very well. Thank you.

@Kiran.

Yes, I agree with your solution. Thanks for this solution.

Detailed Explanation:

Cconsider,
Z is actual distance travelled (when going at 10km/hr).
X is time (Unknown).

Case: 1
travelling at normal speed (10Km/hr).
10Km-----------------@1 hr
ZKm-------------------@X hr

after cross multiplying each other we get;
10X=Z*1 means that 10X=Z---------1)

Case 2:
Travelling at 14Km/hr.
|||y
14Km-------------@1hr.
20+ZKm----------@Xhr.

here, 20+Z means 20Km + Z Km travelled by Normal Speed @ same X hour.

by cross multiplying we get,
14X=20+Z-----------------2)

just solve both equation 1) & 2.
sub 1 in 2
Z=10X ,we get 14X=20+10X.
so, 4X=20 , X=5 now, we are not questioned for hours but only we need distance so,sub X directly in equation 2).

We get 70=20+Z so Z = 70-20 = 50Km.

The actual distance 50km(10km) but he travelled 70km by 14kmph, the question is THE ACTUAL DISTANCE TRAVELLED BY HIM? Is it 70 or 50?

Suppose walking time of this man = t.
So the walking distance for 14kmph = 14 * t = 14t,
and the actual walking distance=10 * t = 10t.

So as question, we can say 14t-10t = 20km # 4t=20 #t=5.

So the actual distance travel by him = 10 * 5 = 50km.

Hope all of you understand.

Why you take x+20 can anyone explain it? Please.