Inequality symbols: a refresher
Photo by Valentin Petkov on Unsplash
Today we are learning about inequality symbols, and easy memory tricks for how to remember them, including the “greedy mouth”.
< means “less than”
3 < 5
You would read that as “3 is less than 5”
You could think of the < like a greedy mouth, gobbling up the bigger value. It would rather have 5 pieces of chocolate over 3 pieces of chocolate. Look at the above photo. See how the mouth looks like the < symbol?
If you saw this:
4 8
Could you put a < in there? Yes!
4 < 8
“4 is less than 8”
The greedy mouth gobbles up the bigger value, so it is gobbling up the 8.
What about this though:
8 4
The greedy mouth still wants to gobble up the 8. It would rather have 8 pieces of chocolate over 4 pieces of chocolate, so it would be
8 > 4
“8 is greater than 4”
> means “greater than”
Put either < or > in each of these below:
9 10
9 8
100 2
9 < 10 9 is less than 10
9 > 8 9 is greater than 8
100 > 2 100 is greater than 2
Let’s introduce a variable, we’ll use x.
If we have this:
x < 2
which of these values could x be worth? Check all that apply!
A. 0
B. 1
C. 2
The answer is A and B, x can be worth 0 or 1 because:
if x < 2
0 < 2: yes, that’s true! x can be worth 0
1 < 2: yes, that’s true! x can be worth 1
2 < 2: no, that’s not true. x cannot be worth 2
Let’s learn two more inequality symbols:
< less than or equal to
> greater than or equal to
A memory trick is this line _ looks like half of an equal sign (=), so it indicates the “or equal to”.
x < 2
which of these values could x be worth? Check all that apply!
A. 0
B. 1
C. 2
Now the answer is A, B, and C. x can be worth 0, 1, or 2 because:
x < 2
0 < 2: yes, that’s true!
1 < 2: yes, that’s true!
2 < 2: yes, that’s true, since 2 is equal to 2, and we have the “less than or equal to” symbol there (<)
One more question:
x > 10
Which of these values could x be worth? Check all that apply!
A. 5
B. 10
C. 15
The answer is B and C, x can be worth 10 or 15, because:
x > 10
5 > 10, that’s not true. The greedy mouth doesn’t want to gobble up the 5!
10 > 10, that is true. (Remember the _ adds ‘or equal to’)
15 > 10, that is true. 15 is greater than 10.
Good job today. To recap:
< less than
> greater than
< less than or equal to
> greater than or equal to
Memory tricks:
The greedy mouth wants to gobble up the bigger value
The line _ looks like an equal sign, so it adds the ‘or equal to’
A few practice problems for you to try!
Put in > or <:
5 3
4 5
x > 15 which of these could x be worth: 13, 14, 15, 16?
x <7 which of these could x be worth: 5, 6, 7, 8, 9?
x > 73 which of these could x be worth: 71, 72, 73, 74?
x < 7 which of these could x be worth: 5, 6, 7, 8, 9?
Answers:
5 > 3
4 < 5
x > 15 which of these could x be worth: 13, 14, 15, 16? x could be worth 15 or 16.
X < 7 which of these could x be worth: 5, 6, 7, 8, 9? x could be worth 5, 6, or 7.
x > 73 which of these could x be worth: 71, 72, 73, 74? x could be worth 74.
x < 7 which of these could x be worth: 5, 6, 7, 8, 9? x could be worth 5 or 6.
Great job!