Grade 1Length, Time and Data1.MD.A.1

Ordering by Length

Compare two things by comparing each to a third.

Not started Jump to practice

In Kindergarten you compared two lengths by lining them up. Now put three things in order, even when two of them can’t touch.

Lined up at the left: from shortest to longest, the order is B, A, C.

Key idea

If A is longer than B, and B is longer than C, then A is longer than C.

Why it works

B works like a measuring helper. A goes past B, and B goes past C, so A must go past C too.

Worked example: Three things

A rug is longer than a towel. The towel is longer than a sock. Which is the longest?
  1. Put them in order: rug, towel, sock.
  2. The rug is the longest. The sock is the shortest.

Answer: The rug

For grown-ups: Use a piece of string to compare two things that can’t sit side by side, like a door and a table.

Practice

Pass with 3 right answers, the last 2 in a row. Each right answer earns 1 XP.

Loading practice…

Builds on

Leads to

Sources and further reading

  • Common Core State Standards for Mathematics, Grade 1, 1.MD.A.1: order three objects by length; compare two lengths indirectly using a third object
  • Institute of Education Sciences practice guide: Assisting Students Struggling with Mathematics: Intervention in the Elementary Grades (WWC 2021006)
@teddyrookbook GitHub