An ‘a' train leaves a subway station every 12 minutes. an ‘e' train leaves every 9minutes. if both trains just left the station on parallel tracks, when will both leave the station together again? a. in 108 minutes b. in 36 minutes c. in 72 minutes d. in 24 minutes

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)