A) 65 km/h |
B) 55 km/h |
C) 60 km/h |
D) 36 km/h |
B) 55 km/h |
Let the constant speed = x
According to the question,
\( \Large \frac{715}{x} - \frac{715}{x+10} = 2 \)
\( \Large \frac{1}{x} - \frac{1}{x+10} = \frac{2}{715} \)
\( \Large \frac{ \left(x+10\right)-x }{x \left(x+10\right) = \frac{2}{715} } \)
\( \Large x^{2}+10x = \frac{10 \times 715}{2} \)
\( \Large x^{2}+10x-3575 = 0 \)
\( \Large x \left(x+65\right)-55 \left(x+65\right) = 0 \)
\( \Large \left(x-55\right) \times \left(x+65\right) = 0 \)
Therefore, x = 55 or x = -65
Ignoring the negative value, we get
x = 55
Therefore, Original speed of the motorcycle = 55 km/h