The girls make up one-third of the campers, so there are 96 /3 = <<96/3=32>>32 girls.
The boys make up two-thirds of the campers, so there are 32 + 32 = <<32+32=64>>64 boys.
There are 32 x 75% = <<32*75*.01=24>>24 girls who want to toast marshmallows.
There are 64 x 50% = <<64*50*.01=32>>32 boys who want to toast marshmallows.
They need 24 + 32 = <<24+32=56>>56 marshmallows.
#### 56