The Long Rods
MATERIAL:
Ten, red wooden rods. The height and width are constant. The lengths
increase by ten centimeters from the shortest rod, which is one
decimeter, to the longest which is one meter. Ten of the shortest rods
would equal the length of the longest rod. The difference in length
between any two consecutive rods is the same as the length of the
shortest rod which is ten centimeters or one decimeter.
PURPOSE:
Further study of size. This time, size varies only along one dimension.
The child judges by sight and touch. This enhances awareness of length
in the environment.
AGE:
2
^{1/2}
to 5 years
PRESENTATION:
The long rods are more difficult than the pink tower or broad stair, and
should only be offered after the pink tower and broad stair are being built
easily by a child.
The teacher spreads a dark green mat on the floor and lets the child
help carry the rods to the mat. The teacher lays the rods at random on
the mat but parallel to each other.
The teacher sits next to the child and shows him or her how to judge the
lengths by sight and touch by taking the first two fingers of the
dominant hand, and feeling the entire length of the larger ones in turn
from one end to the other. Then, the teacher selects the longest by
sight and touch and places it nearly at the top of the mat. The teacher
then selects the next longest rod by touch and sight and places it
touching the longest, making sure the left ends are even. The teacher
continues to select rods in order of length, arranging them with even
ends on the left.
If the child joins in and obviously understands the exercise he or she can
continue alone. Otherwise, the teacher completes the exercise.
The teacher lets the child look at the result for a minute with her,
then mixes the rods and leaves him or her to work alone if the child would like to.
The teacher repeats the demonstration if the child prefers.
SPECIAL CIRCUMSTANCES:
A developmentally delayed child should be given 5 rods, every other
one, at first. The difference between the rods is then 20 cms. The child should
be able to make a success of the exercise with 5 rods. After a time, he or she
will be ready to work with all ten rods.
EXERCISE 1
The child places the rods parallel to each other, but in random order,
on the mat. With the first two fingers of the dominant hand, the child feels
the entire length of the rods. He or she then selects the longest rod and
places it at the top of the mat. Judging by sight and touch the child lines up
the rods with the left sides even.
EXERCISE 2
When the child is doing Exercise 1 easily, the teacher lets him or her build
the sequence and then takes the smallest rod and shows how the
difference in two consecutive rods is the length of the shortest rod.
SELFCORRECTION:
The child can see or feel mistakes.
VOCABULARY:
When the child can sort the rods in order, the teacher can then introduce the vocabulary below as appropriate using the
"Three Period Lesson."
Long  Short
Long  Longer  Longest
Short  Shorter  Shortest
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