3.MD.3 Draw a scaled picture graph and a scaled bar graph to represent data with several categories. Solve one-and two-step "how many more" and "how many less" problems using information presented in scaled bar graphs. For example, draw a bar graph in which each square in the bar graph might represent 5 pets.
Evelyn and Jason surveyed two classrooms to see how many animal pets the children had at home. The data they collected showed that the students had 22 mammals, 14 birds, 4 reptiles, 8 fish, and 2 amphibians.
The class decided to make a picture graph to represent this data.
But how can we organize this information?
The graph would be too wide if each animal picture only represented one animal.
What if each animal picture represents two animals? Twenty-two mammals would need eleven dog pictures and that is still too much!
What if we make each animal picture represent four animals? We can count by fours: 4, 8, 12, 16, 20, 24.
But what do we do if there are twenty-two mammals?
Hector figured it out! We can cut one of the dog pictures in half.
Some of the children were not sure that would work, so Andrew showed everyone that if you cut one of the pictures in half then
4 = 2 + 2.
So half a picture represents two animals.
Maria explains to Jason why this works, and tells him how she made her graph.
Luis did not understand that a picture graph and a bar graph both have to start at the same point on the graph and either grow to the right or grow up.
His turtle correctly represents four reptiles, but is it glued in the right place? In addition, he is counting 11 whole animal squares as the number of total animals. Maybe his partner can help him understand what scale means.
Lupita shows the class how to find the difference of "how many more" mammals there are than fish.
William disagrees. He says, "You are right that there are 22 mammals and 8 fish. but 22 minus 8 equals 14--not 26."
Everyone struggled with #2.
Reptiles (4) + birds (14) = 18 reptiles and birds
And there are only 2 amphibians.
Hector shows the class how many pets the students in both classes have altogether.
Wow, Hector!! We have a lot of pets.