# 1.18: Lesson Eighteen

Difficulty Level: At Grade Created by: CK-12

## Using a Matrix

1. Here is a matrix that we have begun to fill in for you:

Left Column:Words with [d] Right Column:Words with no [d]
Top Row: Words with [t]

voted

today

study

toward

different

Square #1

write

touches

bottle

seventy

perfect

Square #2
Bottom Row: Words with no [t]:

holiday

sudden

board

world

Square #3

laugh

queen

surprise

number

Square #4

2. In Square #1 we put words that have both [d] and [t] sounds, like voted. Find the one word below that has both a [d] and a [t] and copy it into Square #1 beneath the word voted:

\begin{align*}&\text{children} && \text{middle} && \text{today} && \text{fruit}\end{align*}

3. In Square #2 we put words like write that have a [t] but do not have a [d]. Find the word below that does have a [t] but does not have a [d] and copy it into Square #2 beneath the word write:

\begin{align*}&\text{robber} && \text{danger} && \text{touches} && \text{under}\end{align*}

4. What word is in Square #3? holiday

5. Does it have a [d]? Yes Does it have a [t]? No

Why do we put holiday in Square #3? Because it has a [d] but no [t].

Why do we put laugh in Square #4? Because it has neither a [d] nor a [t].

7. Copy these words into the correct squares in the matrix:

\begin{align*}&\text{study} && \text{sudden} && \text{ perfect} && \text{board}\\ &\text{bottle} && \text{queen} && \text{different} && \text{world}\\ &\text{toward} && \text{seventy} && \text{surprise} && \text{number}\end{align*}

7. What direction do columns go on the page? Up and down the page

8. What direction do rows go on the page? Across the page, left and right

Word Scrambles. Unscramble these letters to spell some of the words in this lesson. Some of them are quite hard, so we've left you some doodling space:

\begin{align*}&\text{dudens} && \underline{sudden} && \text{remunb} && \underline{number}\\ &\text{dusty} && \underline{study} && \text{ardob} && \underline{board}\\ &\text{dowart} && \underline{toward} && \text{dahoily} && \underline{holiday}\\ &\text{trafe} && \underline{after} && \text{lahug} && \underline{laugh}\\ &\text{driftneef} && \underline{different} && \text{prerussi} && \underline{surprise}\end{align*}

Teaching Notes.

1. This lesson demonstrates how the matrix can help sort out words on the basis of whether two different conditions (in this case the presence of [d] or [t]) occur together in the word, whether one occurs without the other, or whether neither occurs.

If your arithmetic program has the students working with sets, you could point out that a square in a matrix is a set. So a matrix is a set of sets.

2. The words voted in Item 1 and bottle in Item 6 could raise again the possible confusion caused by the flap-[d]. If a student should ask something like, “I hear a [d] in the middle of bottle, not a [t], so why don't we put it into Square #3 instead of Square #2?,” congratulate him or her for a sharp eye and a good question and remind the class that earlier we agreed that although that sound is a bit like [d] and a bit like [t], we are going to call it [t] because it is spelled <t> or \begin{align*}<\mathrm{tt}>\end{align*} and most dictionaries show it as [t].

3. If you would like to do some additional sorting with this matrix, here are some other words from recent lessons that contain [t] and/or [d] and a few that contain neither:

[d] and [t]: didn't, reddest, wouldn't

[t] only: helicopter, matrix, sister, important, stopped (notice the final [t] spelled <ed>)

[d] only: behind, children, holiday, middle, under

neither [d] nor [t]: penguin, people, column, row

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