we need: 28*3=84

we have:84:25=3(remaining 9)

so we need a packet for these 9  sheets of graph of papers

3+1=4 (packets)

answer:4 packets

The number of sheets of graph of paper that the students need is :

3 x 28 = 84

We have : 84 : 25 = 3 with remainder 9

So we need a packet for these 9 sheets of graph of paper.

 Then the answer is : 3 + 1 = 4