Prep T1-PS-Q51

[kaijen]

51. 6587-!-item-!-187;#058&005111
Circular gears P and Q start rotating at the same time at constant speeds. Gear P makes 10 revolutions per minute, and gear Q makes 40 revolutions per minute. How many seconds after the gears start rotating will gear Q have made exactly 6 more revolutions than gear P ?

(A) 6
(B) 8
(C) 10
(D) 12
(E) 15

Ans:(D)

不好意思 這一題我完全不知如何著手 謝謝

[Enriqueta]

51. 6587-!-item-!-187;#058&005111
Circular gears P and Q start rotating at the same time at constant speeds. Gear P makes 10 revolutions per minute, and gear Q makes 40 revolutions per minute. How many seconds after the gears start rotating will gear Q have made exactly 6 more revolutions than gear P ?

(A) 6
(B) 8
(C) 10
(D) 12
(E) 15

Ans:(D)

不好意思 這一題我完全不知如何著手 謝謝

P每1分鐘轉10次 => 60/10=6秒/次
Q每1分鐘轉40次 => 60/40=1.5秒/次
假設在T秒之後，Q比P多轉了6圈
(T/6) = (T/1.5) - 6
T=12