The time period of simple pendulum is ‘T’ when the length increases by 10cm, its period is T1. When the length is decreased by 10 cm, its time period is T2. When the relation between T, T1and T2 is

time period of simple pendulum is T=2πlgTαl  other terms are constants l=KT2-----(1)    proportionality constant is K,by the question,l+10=KT12----(2)l-10=KT22-----(3)Adding (2) and (3) equations2l=KT12+T22substitute (1)2KT2=KT12+T222T2=(T12+T22)