Latest Elitmus Aptitude Question SOLUTION: a biker notices a certain number(2 digits number) on the milestone before starting the journey. After riding for an hour he notices a milestone with reversed digits of the previous

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(#M40156000) ELITMUS Numerical Ability question Keep an EYE

a biker notices a certain number(2 digits number) on the milestone before starting the journey. After riding for an hour he notices a milestone with reversed digits of the previous number. Now after riding for another hour he notices that the number on a new milestone had same digits as the first one (in the same order) but with a "0" between the 2 digits. If the rider maintains a constant speed throughout, Calculate his speed.

Asked In Elitmus sahil aggarwal (8 years ago)

Solved Anusha Nadakudity Read Solution (11)

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Read Solution (11) :

Subha Mahapatra  (8 years ago)

ANS : 45

let first two digit number is xy = 10x + y
after one hour, the number is reversed yx = 10y + x
after another one hour, it x0y = 100x + y.

now xy < yx < x0y

so, (10y + x) - (10x + y) = (100x + y) - (10y + x)
or, 9(y - x) = 9(11x - y)
or, 12x = 2y

the above equation will be true only if x = 1 and y = 6.

hence, his speed is 45

Is this solution Helpfull? Yes (37) | No (4)  

Anusha Nadakudity  (8 years ago) Best Solution

let the speed be s kmph,and digits x,y
then milestones will be 10x+y,10y+x,100x+y
9y-9x=s;
99y-9y=s;
solving we get s=45x;
y=6x;
since y is a digit x=1;
hence y=6;
s=45 kmph

Is this solution Helpfull? Yes (20) | No (3)  

vikas gupta   (7 years ago)

ANS : 45

first suppose 12
then 21
then 102

difference between 21-12= 9
then difference between 102-21=81

after that add 81+9 = 90
because of total houre 2 so that 90/2= 45
u can choose any number and get the deference then add and
devide by total hour then find speed

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Yogesh Arun Katu  (8 years ago)

first milestone 16
second milestone 61
third milestone 106
speed 45

Is this solution Helpfull? Yes (5) | No (2)  

gkp  (8 years ago)

let
first no. is XY then
second will YX and
last will X0Y

now assume S is speed then we can say that
XY+S=YX (1)
YX+S=X0Y (2)
put 1 in 2 we get
2S=X0Y-XY
now put X and Y any value except 0,0 because speed can't be 0
s=45


so answer is 45

Is this solution Helpfull? Yes (5) | No (2)  

ashish bansal  (8 years ago)

(10y + x) - (10x + y) = (100x + y) - (10y + x)
how this equation comes

Is this solution Helpfull? Yes (4) | No (2)  

Vignesh V  (8 years ago)

YX-XY=X0Y-YX;
X can be only 1 or 2 as deviations from other numbers are huge.
when we plug in the value of x=1 and y=6 in the equation above, we get LHS=RHS=45. which is the constant speed at which he is travelling ie., 45KM/hr

Is this solution Helpfull? Yes (1) | No   

Zeesha Mishra  (8 years ago)

why x=1 and y=6..??

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sahil aggarwal  (8 years ago)

According to me, the speed should be 45. correct me if I am wrong

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shashank jain  (8 years ago)

45 is correct

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Vignesh V  (8 years ago)

XY-YX=YX-X0Y;
X can be only 1 or 2 as deviations from other numbers are huge.
when we plug in the value of x=1 and y=6 in the equation above, we get LHS=RHS=45. which is the constant speed at which he is travelling ie., 45KM/hr

Is this solution Helpfull? Yes | No   

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