Question

A and B started their journeys from X to Y and Y to X, respectively. After crossing each other, A and B completed the remaining parts

of their journeys in 49/8h and 8 h respectively. If the speed of B is 28 km/h, then the speed (in km/h) of A is​

Answer 1

Given :

A stared his journey from point X

B stared his journey from point Y

They cross each other

Time taken by A to cross = $T_1$ = $\dfrac{49}{8}$ hours

Time  taken by B to cross = $T_2$ = 8 hours

The speed of B = $S_2$ = 28 km/h

To Find :

The speed of A

Solution :

Let The speed of A = $S_1$

Both A and B crosses each other then both must cover half distance

Let The Total distance between point X and Y = D km

∵  Distance = Speed × Time

For A

$\dfrac{D}{2}$  = $S_1$  ×  $T_1$

Or,  $\dfrac{D}{2}$  = $S_1$  ×  $\dfrac{49}{8}$                   ........1

Again ,

For B

$\dfrac{D}{2}$  = $S_2$  ×  $T_2$

Or,  $\dfrac{D}{2}$  = 28  ×  8                   ........2

Now, From eq 1 and eq 2

$S_1$  ×  $\dfrac{49}{8}$    =    28  ×  8    

Or,  $S_1$   =  $\dfrac{28 \times 8}{\dfrac{49}{8} }$

            = $\dfrac{28 \times 8 \times 8}{49}$

            = $\dfrac{1792}{49}$

            = 36.5  km/h

∴ B speed = $S_1$  = 36.5 km/h

Hence, The speed of B is 36.5 km/h    Answer

Answer 2

Speed of A = 36.57 km / h (Approx)

Step-by-step explanation:

Given:

Speed of B = 28 Km/h

Time taken by A = 49/8 h = 6.125 h

Time taken by B = 8 h

Find:

Speed of A = ?

Computation:

⇒ Total distance cover by B = Speed of B × Time taken by B

⇒ Total distance cover by B = 28 × 8

⇒ Total distance cover by B = 224 km

⇒ Speed of A = Total distance cover by B / Time taken by A

[∵ Total distance cover by B = Total distance cover by A ]

⇒ Speed of A = 224 / 6.125

Speed of A = 36.57 km / h (Approx)

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