Answer :
Given : Three strings are of lengths 120 cm, 136 cm and 160 cm.
Now we want to cut smaller pieces with equal length . So to find longest string possible we find H.C.F. of all these lengths , As :
120 = 2 2 2 3 5
And
136 = 2 2 2 17
And
160 = 2 2 2 2 2 5
So,
H.C.F. ( 120 , 136 , 160 ) = 2 2 2 = 8
SO,
we can cut longest string of 8 cm ( Ans )