SME
Grade 7 Math · Problem type
Map distances in kilometers
Use this for “On a map, 1 cm represents 5 km. How far is a 7.2 cm route?”
Diagram
d = 7.2 cm on the top line sits over 36 km on the bottom line: each 1 above is 5 below.
This is an example. Type your own values to start a new problem.
a (km)
=
s
×
d (cm)
Formulas
a
=
s
×
d
(actual
distance
=
kilometers
for
1
cm
on
the
map
×
distance
on
the
map)
36 = 5 × 7.2
Assumptions
•
A map scale says what 1 cm on the map stands for: 1 cm represents 5 km.
•
Every distance on the map is multiplied by the same number.
•
Measure the map distance, then multiply by the kilometers for each centimeter.
Step-by-step
WE KNOW
s = 5 (kilometers for 1 cm on the map), d = 7.2 cm (distance on the map)
FIND
actual distance (a)
Step 1 · Find actual distance (a)
Use a = s × d (actual distance = kilometers for 1 cm on the map × distance on the map)
Each
centimeter
on
the
map
stands
for
s
kilometers.
a
=
5
×
7.2
a
=
36
km
Check
Put the numbers back in. Both sides should match.
36 = 5 × 7.2 ✓
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