Science Problems, questions, exercises Study and teaching (Elementary) Study and teaching Mathematics Mathematics--Problems, questions, exercises Mathematics--Study and teaching Science--Study and teaching Botany Study and teaching (Secondary) Ecology--Study and teaching Experiments Mathematics--Study and teaching (Elementary) Physics Science--Problems, questions, exercises Birds Ecology--Problems, questions, exercises Mammals Chemistry Teaching Vocabulary Elementary mathematics. Arithmetic Geometry Language Boots and shoes Botany --Philippines Botany, Medical Dictionaries Dictionaries, Juvenile Earth sciences