Latest Infosys Aptitude Question SOLUTION: A car is travelling at a uniform speed. The driver sees a milestone showing a 2-digit number. After travelling for an hour the driver sees another milestone with the same digits in

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(#M40003079) INFOSYS Numerical Ability question Time Speed and Distance Keep an EYE

A car is travelling at a uniform speed.
The driver sees a milestone showing a 2-digit number.
After travelling for an hour the driver sees another milestone with the same digits in reverse order.
After another hour the driver sees another milestone containing the same two digits.
What is the average speed of the driver.

Asked In Infosys ashutosh singh (12 years ago)

Unsolved Read Solution (5)

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Read Solution (5) :

Rohit Khajuria  (12 years ago)

FIRSTLY, the Question is not complete.
SOLUTION
the first milestone seen by the driver is 2 digited. let it be ... 10x + y ..(1)
After 1 hr
the second milestone is in reversed order. it must be ... 10y + x ....(2)
again after 1 Hr
the third milestone having same digit bt their is zero btween the to digitsit is given as ... 100x + 0*10 + y = 100x + y ....(3)
from eqn 2 and 3, we get
{(100x + y) - (10y + x)}/1 = speed of the car .... {Distance = speed * time}
therefore speed of the car = 99x - 9y .. (4)
from 1 1nd 2 ,we get
9y - 9x = speed of the car ....(5)
from eqn 4 and 5,we get
9y - 9x = 99x - 9y
or y - x = 11x - y
or y = 6x ... (6)
substituting this value in the eqns 1 and 2, we get
10x + 6x = 16x (the first milesztone)
10*6x + x = 61x (the second milestone)
Speed of the car = (distance between two milestone)/time
= (61x - 16x)/1
= 45x km/hr
On seeing the option we can select our answer.
by just putting x = 1,2,3,4,....................

Is this solution Helpfull? Yes (20) | No (2)  

ashutosh singh  (12 years ago)

Here uniform speed is given so
Let assume first milestone will contain =xy
second=yx
third would be the combination of these two so x0y or y0x
Driver travels yx-xy in a hour and x0y-yx or y0x-yx in another one hour
Speed=Distance/Time
(yx-xy)/1=(x0y-yx)/1
{Due to uniform speed}
(10*y+x)-(10*x+y)=(100*x+0*10+y)-(y*10+x)
after solving we'll have x/y=1/6 or y=6x
put the value x=1,2,3.....
for x=1
Speed=61-16=45 Km/Hr

Is this solution Helpfull? Yes (7) | No   

Dr.Dipin Singh  (12 years ago)

milestones are 16,61 and 106
so speed is 45 mph if milestone is giving distance in miles.

Is this solution Helpfull? Yes (5) | No (5)  

dinesh  (12 years ago)

average speed is 25.66km/hr
first he sees 25km milostone
then he sees 52km milestone
and at last he sees 77km milestone.....
25 reverse digit 52 and then same two digit contg. no.

Is this solution Helpfull? Yes (2) | No (7)  

Gangadhara  (9 years ago)

@ashutosh sing
if we put x=1 then y=6, so that first mile stone is 16 km, car speed is 16kmph
given car travelling uniform speed then 2nd milestone at 61 and 3rd 601 impossible (according to question)

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