A blue light flashes every 2 minutes.
A white light flashes every 3 minutes.
At 8 pm they flash together
a) At what time will this happen again?
b) The lights are adjusted at 9:30 pm. at which they flashed together. Now the blue light flashes every 6 minutes and the white light flashes every 10 minutes. At what time will they next flash together?
2007-09-19 13:46:21 · 2 answers · asked by NinjaX 2 in Science & Mathematics ➔ Mathematics
a) 8:06 PM -- if they flash together n minutes after 8 PM, then n must be a multiple of both 2 and 3, and if it is the first time they flash together after 8, then n must be the least common multiple of 2 and 3, which is 6. Thus they flash together 6 minutes after 8, which is 8:06.
b) same method: LCM (6, 10) = 30, so they first flash together 30 minutes after 9:30, which is 10:00 PM.
2007-09-19 13:55:46 · answer #1 · answered by Pascal 7 · 0⤊ 0⤋
a) 8:06 pm
LCM of 2 & 3 = 6
8:00 + 0:06 = 8:06
b) 10:00 pm
LCM of 6 & 10 = 30
9:30 + 0:30 = 10:00
2007-09-19 13:54:16 · answer #2 · answered by Marvin 4 · 0⤊ 0⤋