aptitude

Question

A man drives 25 km in city and then increases its speed by one fourth of its original and reaches its destination 40 mins early..if he had done the same 10 km earlier it would have saved another 5 min...find total distance travelled by car?

Answer 1

Let (x+25)Km is total distance , t hr is time to reach the destination with speed s km/h 

so time = distance/time 

(x+25)/s  = t    ---------------(i)

if after 25km he increase his speed by 1/4 of original ,i.e, with 1.25s km/h , he reach his destination 40 min early , i.e 40/60 hr early,i.e, he takes (t - 40/60) hrs

25/s + x/1.25s = t - 40/60    --------(ii)

if after 15km he increase his speed by 1/4 of original ,i.e, with 1.25s km/h , he reach his destination 45 min early , i.e 45/60 hr early, i.e, he takes (t - 45/40) hrs

15/s + (x+10)/1.25s = t - 45/60   -----(iii)

subtract (iii) from (ii)
10/s -10/1.25s = 5/60

s = 24 km/h 

subtract (ii) from (i)

x/s - x/1.25s = 40/60

x = 10s/3 = (10 * 24)/3

x = 80 km 

Total distance = x+ 25 km = 80 +25 km = 105 Km .
 

Comments

According to second condition distance travelled at original speed will be 25-10=15

SO final ans will be 25+80=105

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Yes

Answer 2

Here see the logic for every 10 kilometers 5 minutes covered. For this we have 40 minutes covered

that means 40/5=8

and 8*10=80 kilometers covered and intially with constant speed we covered only 25 kilometers

so 25+80=125 kilometers.