Starting from his house one day a student walks at a speed of 2and 1/2 kmph and

Question

Starting from his house one day a student walks at a speed of 2and 1/2 kmph and reaches his school 6 minutes late next day he increases his speed by 1 kmph and reaches the school 6 minutes early

 

 

take x as time

time speed dis chart

 

            D =             S       *      T

first                         5/2    *      x-1/10

second                    7/2     *      x+1/10  

 

how x-1/10 come they gave speed in kmph so time is also in hours so 6/60 is 1/10

distance is equal

 

equation

5/2*x-1/10=7/2*x+1/10

 

10x-1/4=70x+7/20

x=-10

 

i put in x it goes wrong 

answer is 1and3/4 km

 

please explain where i goes wrong

 

 

 

 

Answer 1

Let the distance between his home and school be 'x',then
The time taken by him when he travels at a speed of 2.5km/h be T1
and the time taken by him when he travels at a speed of 2.5 +1=3.5km/h

T1 = x/2.5
T2 = x/3.5 and
T1 - T2 = 12 mins ( 6+6=12)  i.e.12/60 hrs

(12/60) = x/2.5 - x/3.5

1/5 = 1x/(2.5)(3.5)

1/5 = 1x/8.75

 

8.75 =5x   ( cross multiplication)

 1.75= x



Thus the distance between his home and school is equal to 1.75 km = 1   3/4  km