The relation is T α √(l/g)

Hence if lenght is four times, time period is 2 times..
and if g is 1/4 times time period is 2 times
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T =2π√l/g    ie T the period is directly proportional to the squre root of  l the length of the string and inverselyproportional to g the accelaration due to when length is doubled,period will be increased by 2 times. when the accelaration due to gravity is reduced by 1/4th ,then period is inncreased by 2 times