Question

Which of the following has a terminating decimal expansion? 

(a) 32/91 (b) 19/80 (c) 23/45 (d) 25/42

Answer 1

(b) 19/80

19/80 = 19/2⁴ x 5

We know 2 and 5 are not factors of 19, so it is in its simplest form. 

And (2⁴ × 5) = (2^m × 5ⁿ ) 

Hence, 19/80 is a terminating decimal.