The answer is correct because a complete oscillation is made when it reaches back at r
but it reaches the mean position so calculating.....
one quarter oscillation is 1.2/3 =0.4sec
therefore four parts would be 0.4*4=1.6sec
time period is equal to one to and fro osc

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How one quarter oscillation is 1.2/3?
because the bob has oscillated 3/4 of it hence one third would be one part of the 3