Question

from a piece of rope 20m long , 100 pieces each of 7.5 cm long are cut off; how much of the rope remains

Answer 1

100*7.5=750cm=7.5 m
left rope=20-7.5=12.5m

Answer 2

20 m - 100 * (7.5/100) m
= 20m - 7.5
= 12.5

:-)