Question

Correct answers only please!

Answer 1

Answer:

  C. 67 mph

Step-by-step explanation:

The speedometer reports speed based on the number of revolutions the tire makes in a given time period. If the motorcycle travels 28/25 times as far on each revolution, its speed is 28/25 times as great.

  (28/25)(60 mph) = 67.2 mph ≈ 67 mph

_____

The distance traveled is proportional to the circumference of the tire, which is proportional to the diameter. Hence, actual speed for a given speedometer reading is proportional to the diameter of the tire.

Answer 2

Answer:

C. 67 mph

Step-by-step explanation:

∵ The ratio of speed of motorcycle and the circumference of the tyre is constant for a motorcycle,

If x be the speed ( in mph ) of a motorcycle having the tyre of diameter 28 inches,

⇒ The ratio of speed and circumference = $\frac{x}{2\pi (14)}$

( Because radius = Diameter / 2 ),

While, the speed of the same motorcycle having the tyre of diameter 25 inches is 60 mph,

⇒ The ratio of speed and circumference = $\frac{60}{2\pi (12.5)}$

By the above statement,

$\frac{x}{2\pi (14)}=\frac{60}{2\pi (12.5)}$

$\implies x=\frac{60\times 14}{12.5}=\frac{336}{5}=67.2\approx 67$

So, the actual speed of the motorcycle after changing the tyre is 67 mph ( approx )

Hence, option 'C' is correct.