sandy wrote:
Carlos runs a lap around the track in x seconds. His second lap is five seconds slower than the first lap, but the third lap is two seconds faster than the first lap. What is Carlos’s average (arithmetic mean) number of minutes per lap, in terms of x?
(A) \(x - 1\)
(B) \(x + 1\)
(C) \(\frac{x-1}{60}\)
(D) \(\frac{x+1}{60}\)
(E) \(\frac{x+3}{60}\)
Such questions, substituting some value for X is another good waySo let X be 5 secs...so first lap in 5, second in 5+5 and third in 5-2...
Thus 3 laps in 5+10+3=18 seconds, but our answer is in minutes, so the average is 18/3=6 secs or 6/60 minutes..
Look at the choices..
D is (x+1)/60=(5+1)/60=6/60
D