A particle in SHM has a period of 4 sec. It takes time t1 to start from mean position and reach half the amplitude in another case it takes a time t2 to start from extreme position and reach half the amplitude, then
SHM can be described by the equation x=Asin(2πtT)
t=0,x=0
x=A/2 at time t = 2πtT=π6 => t=T12
x=A at time t = 2πtT=π2 => t=T4
So time to move from mean position to half of amplitude, t1=T12 s
Time to move from extreme to half of amplitude = time to move from half of amplitude to extreme =t2=T4−T12=T6
Therefore t1t2=12
Answer. B