Question

How to solve marked example step by step explanation please...

Answer 1

Answer:

Step-by-step explanation:

let us consider x = A and y = B

let speed A = x km /h and speed of B = y km/h

time = distance / speed

time taken to cover 30 km by A = 30/x

                                              B = 30/y

given time taken by A = time taken by B + 3

time taken by A - 3 = time taken by B

30/x - 3 = 30/y

30 - 3x /x = 30/y

30y - 3xy = 30x

30y  - 30x = 3xy

30x - 30y = - 3xy

10x - 10y = -xy ....... i

when A doubles his speed

time taken by A + 3/2 = time taken by B

30/2x + 3/2 = 30/y

15/x + 3/2 = 30/y

30y + 3xy = 60x

10y + xy = 20x

20x - 10y  = xy ....... ii

10x - 10y = -xy  from  i

10x = 2xy

y = 5

10x - 50 = - 5x

15x = 50

x=50/15 = 10 / 3

Hence speed of A = 10/3 km/h

               that of B = 5 km/h

Hope it helps you ..

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