Texas Math Models

Try “number line” or “4.5D”

TEKS 4.5A · Grade 4

Drawing a word problem before solving it

Turning a multi-step problem into a strip diagram and an equation with a letter for the part you do not know yet.

The standard itself reads: “4.5A: represent multi-step problems involving the four operations with whole numbers using strip diagrams and equations with a letter standing for the unknown quantity”

One of them, worked all the way through

The Student Exemplar page for question 1: A club has 6 teams with 9 members each. 14 are absent. Which equation finds how many are present? The correct answer is marked, and the question is worked out underneath.
  1. Six teams of nine is 6 x 9.
  2. Fourteen are missing, so those come off.
  3. Write it as ONE sentence with a letter for the part you do not know: (6 x 9) − 14 = m. The parentheses make the multiplying happen first.

This is one way, not the only way. The printable shows the same question worked more than one way, because children get there differently.

What usually goes wrong, and what helps

Each of these is a different misunderstanding rather than a slip, so each one needs something different. Find the one that sounds like your kid.

The student writes an equation with the answer already in it instead of a letter for the unknown
The letter stands for what you do not know yet. If the answer is already written into the equation, there is nothing left to find.
The student adds where the story repeats an equal amount, which is what multiplying is for
Six teams of nine is nine, six times over. Adding 6 and 9 gives you one team and a bit.
The student adds the absent members instead of taking them away
Ask what the story does to the 14: do those members join the club that day, or leave it? Adding and taking away cannot both be right.

Try this at home

Ask what the letter stands for out loud. If they can say 'm is how many are left', the equation almost writes itself; if they cannot, the equation will not be right whatever it looks like.

where these methods come from The strategies behind it: the Strip diagrams chart.

What’s in the printable

Four questions on this skill, two to a page. The rest of the file is for the adult: an answer key, a worked solution for every question, and teacher pages on what each wrong answer means. 10 pages in all.