26
Scale
Textbook, pp. 115–120
GoalUnderstand scale; convert distances between maps or drawings and real sizes.
New words
scale · masshtabmap · xaritadrawing / plan · chizmareal size · haqiqiy o‘lcham
Explanation
Scale is the ratio of a size on the drawing to the real size. If the scale is 1 : 100,000, then 1 cm on the drawing is 100,000 cm = 1 km in reality. A distance on the drawing is directly proportional to the real distance, so real distance = drawing distance · the scale denominator. To show small things enlarged we use a scale such as 5 : 1: the drawing is 5 times bigger than the real object. The smaller the scale denominator, the larger the drawing.
Worked examples
On a map 4 cm, scale 1 : 500,000: in reality 4 · 500,000 = 2,000,000 cm = 20 km.
If an insect drawing at scale 5 : 1 is 15 mm, the real length is 15 : 5 = 3 mm.
Class activity
“Classroom plan”: groups draw the classroom at scale 1 : 50: they measure the length and width and reduce them by the scale. Then other groups recover the real sizes from the plan.
Practice
1
Scale 1 : 1000. A 6 cm distance on the plan is how many metres in reality?
60
2
Scale 1 : 200,000. The real distance is 18 km. How many cm on the map?
9
3
An insect drawn at scale 5 : 1 measures 15 mm. What is its real length in mm?
3
4
Which scale gives a bigger drawing, 1 : 50 or 1 : 500? Why?
1 : 50. The real size is reduced 50 times, not 500 times, so the drawing is bigger.