The school decided to carry out the activity of "reciting ancient poems" in two classes of grade six, requiring each student to buy a "ancient poem reader" with a unit price of 5 yuan.

If you buy according to the actual number of people, you need to spend:

(48+49)×5×( 1- 10%),

=97×5×90%,

=436.5 yuan.

If you press 100, you need to spend:

100×5×( 1- 15%),

= 100×5×85%,

=425 yuan.

Since 425 yuan is less than 436.5 yuan,

So it's more cost-effective to buy one hundred copies.