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Expressing More Relationships Between Numbers
Expressing More Relationships
Between Numbers
CA GR7 AF 1.4
It is very useful to use signs which
indicate relationships between numbers. When we see these signs we
know immediately what the relationship is between the two
quantities.
The sign you are most familiar with is the
equal sign (=). When we see, we know that the quantity to the left
of it is exactly the same as the quantity to the right of it. For
example, 5' = 5'
or 3' + 2' = 5'
.
Now, we can use the equal sign to solve
problems if we can show how an unknown quantity is related to a
known quantity:
- x ft.+ 5 ft. =
8 ft.
By inspection you can see that x
must be 3 because the total on the left side (x
ft. + 5
ft.) must equal the total on
the right side (8 ft.).
Here are some other signs which you should
be familiar with, even though you will not use them as often as
the equal sign. You have undoubtedly seen them before..
- > means is greater than
- 9 > 6
and is read 9
is greater than 6.
- Read these: 10
> 9, x + 2 > x
Notice that the point of the sign is always
toward the smaller number. The expressions were: 10
is greater than 9
and x
plus 2
is greater than x.
- < means is less than
- 4 < 7
and is read 4
is less than 7.
- Read these: 3
< 5, a < a +
7
Notice that the point of the sign is always
toward the smaller number. The expressions were: 3
is less than 5,
and a
is less than a
plus 7.
lf you wanted to express the fact that all the students in class
were 6
feet tall or less, you could write: c
 6'
(where c
represents the approximate height of any student in the class).
-
means is greater than or equal to
- x
5 is read x
is greater than or equal to 5.
- Read this: x
+ 4
4. You should read x
plus 4
is greater than or equal to 4.
-
means is less than or equal to
- x
6
is read x
is less than or equal to 6.
- Read this: x
4 +
2a. This one reads x
is less than or equal to
4
plus 2a.
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1 Problems
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