The length of the longest tape in cm which can be used to measure exactly, the length 100cm; 2m25cm; and 7m80cm is: Pick
A) 30 B) 5 C) 10 D) 36 E) 25

Rationale: the three lengths in cm are 100 , 225 & 780 . hcf of 100 , 225 & 780 is 5 . hence , the answer is 5 cm . answer : b
Answer: B