30
Trial and Improvement
Junior high school
• • • • • • • • • • • • • • • • • • • • • Objective • • • • • • • • • • • • • • • • • • • • •
Mentally estimate and approximate solutions to numerical calculations.
Understand and use the concept of place value in decimals and relate it to computation.
• • • • • • • • • • • • • • • Explanation of the activity • • • • • • • • • • • • • •
Use “trial and improvement” to find the length of the side of a cube-shaped box that can hold
1
00
cm
3
of ice cream.
The two mental calculations 4 x 4 x 4 = 64 and 5 x 5 x 5 =
1
25 should suggest a possible starting
calculation such as 4.5 x 4.5 x 4.5 = 9
1
, which can be shortened to 4.5
3
= 9
1
.
This activity gives students the opportunity to enhance their understanding of decimals and im-
prove their skills in estimation.
• • • • • • • • • • • • • • • • • Using the calculator • • • • • • • • • • • • • • • • •
Calculator functions used: Multiplication, FSE, TAB
Set the calculator to “fixed point” notation with a TAB
value of 0.
(Doing this will display answers to the nearest whole number.)
Adjust the TAB setting to
1
and then continue to improve
the accuracy of the answer
1
4
4
4
5
5
5
4.9
4.9
4.9
•
•
•
4.7
4.7
4.7
4.6
4.6
4.6
From this we can see the answer lies between 4.6 and
4.7. Continue to search for the answer repeating this
operation.
•
•
•
Press the following buttons and then start operation.
DEG
F I X
DEG
4.642X4.642X
F I X
DEG
4.6X4.6X4.6=
F I X
DEG
4.7X4.7X4.7=
F I X
DEG
4.9X4.9X4.9=
F I X
DEG
5X5X5=
F I X
DEG
4X4X4=
F I X
DEG
Summary of Contents for EL-531RH
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