ravi singh   12 years AGO

answer is 7km/hr

let time taken by B is T hr then speed of B is 42/T km/hr

and time and speed of A is T+1 hr and 42/(T+1) km/hr

and if speed of A is double then the time taken by A is half

according to the question,
(T+1)/2 = T-2.5
=>T=6

hence speed of B is 42/6=7km/hr

Like? Yes (6) | No (1)  

manasa epuru   12 years AGO

let time of B be x .. s=d/x
1st case s=d/x+1
2nd case 2s=d/x-2.5
on equating we get x=6 1.e time taken by B
s=d/t.. s=42/6=7.

Like? Yes (5) | No (3)  

Aditya C S   12 years AGO

let x be time taken by to travel 42 km B. Speed of B is Sb
X = (42/Sb)
x+1 = (42/Sa)

X-2.5 = (42/2Sa)

solving X, Sa, Sb. Sb = 7km/hr

Like? Yes (2) | No   

ch.jyothsna   12 years AGO

let time taken by A be x hrs then B takes x-1 hrs.speed of A=42/x Speed of B=42/x-1
let B takes yhrs when A doble his speed then A takes y-2.5 hrs time then A distance is (42*2*(y-2.5))/x = 42 we will get equ 84y-210=42x we know that speed of B is same in two cases so 42/x = 42/y-1 hence x = y+1 substitute this in equ we get y= 6 speed of B = 42/6 = 7km/hr

Like? Yes (3) | No (2)  

Madhu pericherla   12 years AGO

Speed of X = 6 kph
Speed of Y = 7 kph

Speed x / Speed y = a/a+1
2 Speed x/ Speed y = a/a-2.5
Find a = 6hrs
So, speed of y = 42/6 = 7 kph

Like? Yes (3) | No (3)  

Abhishek   12 years AGO

Speed of A = 6 kph
Speed of B = 7 kph

Speed A / Speed B = a/a+1
2 Speed A/ Speed B = a/a-2.5
Find a = 6hrs
So, speed of B = 42/6 = 7 kph

Like? Yes (1) | No (1)  

abhishek ranjan   12 years AGO

Speed a / Speed b = x/x+1
2 Speed a/ Speed b = x/x-2.5
Find x = 6hrs
So, speed of b = 42/6 = 7 kph

Like? Yes (1) | No (1)  

ashiwani kumar singh   12 years AGO

ans:let b take x hours then a takes x+1 hours.
if a have increase the speed its double then takes half time to reach destination..

so (x+1)/2=x-2.5
x=6
then b speed=42/6=7km/h.

Like? Yes (1) | No (1)  

KUNAL GAURAV   12 years AGO

Let speed of A = a km/h
Let speed of B = b km/h

According to the question:
42/a - 42/b = 1
42/b - 42/2a = 2.5

On solving above 2 equations
We get a = 6 and b=7

So,b=7 is the correct answer.

Like? Yes (1) | No (1)  

Chandni Maurya   12 years AGO

ans=(5).7km/hr
let x and y be the speed of A and B, t is the time taken by B,
distance=speed x time
42=x*(t+1) ---1
42=y*t ----2
42=2*x*(t-2.5) ----2
1/2
=>42/42=(x(t+1))/(2x(t-2.5))
=>1=(t+1)/(2t-5)
=>t=6
put t in 2
42=y*6
=>y=42/6=7km/hr

Like? Yes (1) | No (1)  

Alok Kumar   12 years AGO

taking B as a reference frame
let timsie taken by A in first case is t
then when it double its speed t -3.5
let speed of A is A in first case
so
A/2A = (t-3.5)/t
t = 7
so time taken by b = 7-1 = 6hr
so speed of B = 42/6 = 7 km/h

Like? Yes (2) | No (2)  

Raju Sharma   12 years AGO

speed of a=x
then 42/x-42/2x=3.5
solve the x=6
let speed of b=y
42/x-42/y=1
after solve y=7

Like? Yes (1) | No (1)  

rahul jha   12 years AGO

EQUATION WOULD BE LIKE THIS..
speed of A=X
speed of B=Y,time taken by B=t
so,
X(t+1)=Yt.....(1)
2x(t-2.5)=Yt....(2)
equating left side part we get,
t=6 hr
Y=42/6=7km/hr

Like? Yes (1) | No (1)  

Rashmi bharti   12 years AGO

let speed of A=x km/hr and B=y km/hr
then time taken by both of them to cover 42 km is:
A=42/x,B=42/y.
Now given that,
42/x=(42/y)+1 ---(1)
Also given that if A doubles his speed i.e, 2x then
42/y=(42/2x)+2.5 ---(2)
By solving both equation we get,x=6km/hr and y=7km/hr i.e,Speed of B is 7km/hr.

Like? Yes (1) | No (1)  

Dipak Shaw   12 years AGO

Let the time taken by B is x, then A will take (x+1)
so, speed of A = (42/(x+1))
speed of B = (42/x)
From 2nd condition,
2*(42/speed of A) = (42/speed of B)- 2.5
After Solving,we get x= 6;
Therefore, Speed of B = 42/6 = 7km/hr

Like? Yes (1) | No (1)  

vyshnavi   12 years AGO

let speed of A=a
speed of B=b
time taken by B to reach 42 km =t
time taken by A to reach 42km=1+t
if A doubles speed then s=2a
then time taken by A=t-2.5
as we know d=s*t
we equiate a(1+t)=2a(t-2.5)
on solving t=6 hrs
substitue in d=s*t i.e,42=b*6
b=7km/hr

Like? Yes (2) | No (2)  

siddanth   12 years AGO

42/vb=t; 42/va=t+1;
42/2va=t-2.5;substitute 42/va as t+1
i.e (t+1)/2 = t-2.5
t=6
vb=42/6=7

Like? Yes (1) | No (1)  

mohini gupta   12 years AGO

let speed of A be x and time taken is y.
hence, x*y=42
speed is doubled and time reqd is y-3.5.
hence, 2*x+(y-3.5)=42
solving,y=7
time taken by B is 7-1=6.
speed =42/6=7 km /hr

Like? Yes (1) | No (1)  

Parthiban C   12 years AGO

x/y=6/7, so y=7

Like? Yes (1) | No (1)  

Abhishek misra   12 years AGO

speed = distance/time
2*42/(t+1)=42/(t-2.5)
2(t-2.5)=t+1
2t-5=t+1
t=6
speed of b=42/6=7km/hr

Like? Yes (1) | No (1)  

FRANKLIN VIJAY   12 years AGO

Speed of a = 6 kph
Speed of b = 7 kph

Speed a / Speed b = a/a+1
2 Speed a/ Speed b = a/a-2.5
Find a = 6hrs
So, speed of b = 42/6 = 7 kph

Like? Yes (2) | No (2)  

Vaibhav Mishra   12 years AGO

from the 1st situation the eqns formed are
let speed of A as x and speed of B as y
y*t=42,x*(t+1)=42
from 2nd situation the eqns are
y*t=42,x*(t-2.5)=42
now dividing the 1st eqn
x/y=t/t+1
now dividing the 2nd eqn
x/y=t/2(t-2.5)
now putting x/y from 1st eqn into x/y of 2nd eqn
we will get t=6hrs so speed of B y=42/6
y=7km/hr ans.

Like? Yes (4) | No (4)  

Ashutosh Anshu   12 years AGO

Speed of X = 6 kph
Speed of Y = 7 kph

Speed x / Speed y = a/a+1
2 Speed x/ Speed y = a/a-2.5
Find a = 6hrs
So, speed of y = 42/6 = 7 kph

Like? Yes (1) | No (1)  

komal   12 years AGO

Speed a/ Speed b = a/a+1
2 Speed b/ Speed b = a/a-2.5
Find a = 6hrs
So, speed of b = 42/6 = 7 kph

Like? Yes (1) | No (1)  

Suman Saurabh   12 years AGO

Let B takes x hr to walk.
so A takes x+1 hr to walk
so, (x+1)/2+2.5 = x
x=6
speed of B = 7 km/hr

Like? Yes (1) | No (1)  

praneeth   12 years AGO

v1*(t+1)=v2*t;
2*v1*(t-2.5)=v2*t;
on solving the above two equations,we get t=6
it is given that A has taken 1hr more to walk 42 km.so 42=v2*t;therefore,v2=42/6=7 km/hr

Like? Yes (1) | No (1)  

ShAg   12 years AGO

initially let time taken by B=x and then time for A=(x+1)
as distance=42km, speed of B=42/x and that of A=42/(x+1)
now speed of A is doubled=84/(x+1), and its time becomes (x-2.5), so the distance is given by (84/(x+1))*(x-2.5) i.e.;
(84/(x+1))*(x-2.5) = 42
=>x=6
hence as speed of B = 42/x = 42/6 = 7km/hr

Like? Yes (1) | No (1)  

vinodkumar   12 years AGO

Speed of X = 6 kph
Speed of Y = 7 kph
Speed x / Speed y = a/a+1
2 Speed x/ Speed y = a/a-2.5
Find a = 6hrs
So, speed of y = 42/6 = 7 kph

Like? Yes (1) | No (1)  

Shweta Daas   12 years AGO

42/sA=42/sB+1......(1)
42/2sA=42/sB-2.5......(2)

(1)-(2)

42/sA(1/2)=1+2.5
sA=42/(3.5*2)
sA=6

in(1)
42/6=42/sB+1
7-1=42/sB
sB=42/6
sB=7

Like? Yes (1) | No (1)  

Anantharaman   12 years AGO

Substituting values

Assume x=7
B travels 7 km/hr
B reaches in 6 hrs
A reaches in 7 hrs (Given A=>x+1)

If A doubles his speed
A reaches in 3.5 hrs
which is 2.5 hrs ahead of B (x=6)

Like? Yes (1) | No (1)  

jaswinder   12 years AGO

first we should calculate time taken by B for the same distance and then find speed because time taken by A is given in terms of B.
ratio of A's earliar speed to its new changed speed..

Like? Yes (1) | No (1)  

Jasmine Khan   12 years AGO

assume that t1,d1&s1 and t2,d2&s2 be the time distance and speeds of A & B respectively.
given that,
t1=(x+1)hr if t2=xhr......(1)
d1=d2=42km
s1=y1 & s2=y2
now according to the second condition
t1=x-2.5 if t2=x
d1=d2=42km
s1=2y1 & s2=y2
consider,
2y1=42/(x-2.5).....(2)
from (1) and (2)
84/(x-2.5)=42/x+1
after solving we get,
x=6 and x+1=7
speed of B=42/6=7km/hr

Like? Yes (1) | No (1)  

Mariappan   12 years AGO

Sa=42/(Tb+1)

2Sa=42/(Tb-2.5)

therefore,

42/(Tb+1) = 21/(Tb-2.5)

=> Tb=6

Sb=42/6

=>Sb=7 kmph (Speed of B)

Like? Yes (1) | No (1)  

Mayuresh Srivastava   12 years AGO

Let speed of A and B be a and b.
Time taken by b be x hours.
x=42/b---(i)
x+1=42/a---(ii)
x-2.5=42/2a---(iii)
on solving b=7km/hr,a=6km/hr.

Like? Yes (1) | No (2)  

Dr.Dipin Singh   12 years AGO

If A and B are their respective speeds, then

42/A = 1+42/B
42/2A= (42/B)-2.5


solving these eqns, we get
B= 7 km/hr

Like? Yes (2) | No (3)  

DILIP KUMAR   12 years AGO

Disttance : 42 Km
Let speed of B = x km/h
Let speed of A = y km/h
Time taken by B = 42/x h
Time taken by A = 42/y h
Since A takes 1 hr. more
(42/x)+1 = (42/y)
Solving we get
42x-42y-xy=0 ........ (i)

When Speed of A is doubled
speed of A = 2y km/h

Since A arrives 2.5 hrs ahead of B now

(42/x)-2.5 = (42/2y)
Solving we get
42x-84y+5xy ...........(ii)

Subtracting ii from i
we get
42y-6xy=0
6y(7-x)=0
i.e either 6y=0 or 7-x=0
Since Speed of A (y) cannot be zero.
So 7-x=0
x=7
Hence Speed of B = 7 Km/h
Ans : 5) 7Km/h

Like? Yes (2) | No (3)  

richa ahuja   12 years AGO

let time taken by b is x hr
therefore a will take x+1 hr
thus speed of a will be 42/(x+1)
and speed of b will be 42/x
when a doubles his speed then,
2(42/x+1)*(x-2.5)=42 (distance=speed *time)
solving this ,we get x=6
now speed of b is 42/6= 7km/hr

Like? Yes (3) | No (4)  

sanjay kumar saha   12 years AGO

t-(t+1)/2 = 2.5
t=6
speed of B = 42/6 =7

Like? Yes (6) | No (7)  

Raghuram Parvataneni   12 years AGO

let speed of A be x and speed of B be Y
difference in times of A and B is 1hr
hence (42/x)-(42/y)=1;
speed of A is doubled hence equation becomes

(42/2x)-(42/y) = -2.5;

solving we get x= 6 and y=7;

hence speed of y is 7kmph

Like? Yes (1) | No (2)  

Satyendra Singh   12 years AGO

because here equation will be as
(t+1)s1 = s2*t___(1)
2s1(t-2.5) = s2*t __(2)

here s1 is speed of A and t time taken and s2 is speed of B so just soleve these equation and then
d = s*t where d is 42 km so ans will be 7km/hr

Like? Yes (1) | No (2)  

Shuvankar Ghosh   12 years AGO

let the speed of A is x km/hr.
so,42/x-42/2x=2.5+1
hence x=6;
so,speed of B is 42/(42/6-1)=7

Like? Yes (1) | No (2)  

Shubham Kumar   12 years AGO

since A doubles his speed,time taken will be half,so he is saving half of his time i.e T/2.and saving time=time difference ..s0 T=2*3.5=7
so time of A=7 hrs and B=7-1=6 hrs..now distance=42..so speed of B=42/6=7.

Like? Yes (2) | No (3)