Practice
1.1. Practice
a) Measure the straight line on the ground
To measure the length of a straight line (not too long) on the ground, people often use a tape measure.
For example : Measure the length of line segment AB on the ground.
We can do the following:
 Fix one end of the tape measure at point A so that the zero mark of the ruler coincides with point A.
 Straighten the tape measure until point B.
 Read the measurement on the line that coincides with point B. That measure is the length of line segment AB.
B) Align the stakes on the ground.
It is common to use alignment stakes to determine three points of alignment on the ground (see figure).
1.2. Practice (continued)
For example : A friend measures the length of line segment AB on the ground by 20cm. Draw that line segment AB on the map at scale 1:400.
We can do the following:
 Change 20m = 2000cm.
 Calculate the length of line segment AB on the map:
2000 : 400 = 5 (cm)
 Draw a line segment AB of length 5cm on the map.
1.3. Solve the exercises Textbook Practice page 159
Lesson 1: Measure the length and then write the measurement results in the box
Table length 
Width of the classroom 
Length of the classroom 


Solution guide:
 Use a ruler to measure and record the results in the table.
For example :
Table length 
Width of the classroom 
Length of the classroom 
2 m 
7m 
12m 
Lesson 2: I walked 10 steps straight along the schoolyard from A to B
– How many meters long do you estimate line segment AB?
– Please check by using a tape measure to measure the length of line segment AB.
Solution guide:
 Take 10 steps along the schoolyard to make it straight, then estimate how many meters the line from A to B is and check with a tape measure.
Solution :
Take 10 steps along the schoolyard to make it straight, then estimate how many meters the line from A to B is and check with a tape measure.
For example, each step you take about 20cm, from point A to point B in 10 steps will have a distance of:
10 × 20 = 200cm = 2m
1.4. Workbook Solution Practice (continued) page 159
Lesson 1: The length of the classroom board is 3m. Draw a line showing the length of the map on a 1:50 scale map.
Solution guide:
 Change 3m = 300cm (or 3m = 3000mm).
 Calculate the length of the table length on the map we take 300cm divided by 50 (or take 3000mm divided by 50).
 Draw a line with the length calculated in the previous step on the map.
Solution
Change 3m = 300cm
The length of the table length on the map is :
300 : 50 = 6cm
Draw a line segment of length 6cm on the map. That is the line showing the length of the map on a 1:50 scale map.
Lesson 2: The background of a classroom is a rectangle with length 8m and width 6m. Draw a rectangle representing the background of that classroom on a 1:200 scale map.
Solution guide:
 Convert length and width measurements to centimeters.
 With a 1:200 scale map, to find the lengths on the map of the edges, we take the actual lengths of those edges (with the unit of measurement being centimeters) divided by 200.
 Draw a rectangle with the dimensions found above.
Solution
Exchange 8m = 800cm, 6m = 600cm
The length of that classroom floor on the map is:
800 : 200 = 4(cm)
The width of that classroom background on the map is:
600 : 200 = 3(cm)
Draw a rectangle 4cm long and 3cm wide. That’s the rectangle representing that classroom background on the 1:200 scale map.
.
=====
Leave a Reply