Reading a Table

A teacher asks a class how many books each student read last month and records the answers in a frequency table:

Each row is one answer and how many students gave it. The row 1 and 8 does not mean that one student read 8 books: it means 8 students read 1 book each. Reading the column headings first tells you which way round the numbers go.

To answer a question, find the rows it is about. How many students read at least 3 books? At least 3 means 3 or more, so the rows for 3 and 4 books: 4 + 2, which is 6 students. Every student sits in exactly one row, so the whole Students column adds up to the class: 3 + 8 + 6 + 4 + 2 is 23.