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Function Tables 2


This topic continues the topic of function tables.
To review the basics of function tables, see here.


Example 1: Apply the rule

Use the given rule to fill in the missing values.
y = x ÷ 4
Input (x)Output (y)
24
4
8
36

Find the missing y values, substitute the input values for x in the rule ( y = x ÷ 4).
24   →
  24 ÷ 4  
→   6
4   →
  4 ÷ 4  
→   1
36   →
  36 ÷ 4  
→   9

To find the missing x value, solve for y.
y=x ÷ 4
8=x ÷ 4
8 × 4=x ÷ 4 × 4
32=x
So the answer is
y = x ÷ 4
Input (x)Output (y)
24
4
2
36


Example 2: Word problem

Fill in the missing values and find the rule that applies to the table. Write the rule in the format "y = ".
Maria has 5 more cookies than Jeremy.
Rule:
# cookies Jeremy has (x)# cookies Maria has (y)
9
7
8
1

1.   Find the rule

Translate the sentence into an algebraic expression.
Maria has 5 more cookies than Jeremy
Number of cookies Maria has is 5 more than the number of cookies Jeremy has
y = + 5 x
So the rule is y = x + 5.
2.   Apply the rule
To apply the rule ( y = x + 5), substitute the input values for x in the rule.
9   →
  9 + 5  
→   14
7   →
  7 + 5  
→   12
8   →
  8 + 5  
→   13
1   →
   1 + 5  
→   6
So the answer is
Rule:
# cookies Jeremy has (x)# cookies Maria has (y)
9
7
8
1


Example 3: Word problem

Fill in the missing values and find the rule that applies to the table. Write the rule in the format "y = ".
Octagons have 8 sides.
Rule:
Number of octagons (x)Number of sides (y)
8
3
6
2

1.   Find the rule

Translate the sentence into an algebraic expression.
This is a rate problem where the rate is 8 sides per octagon.
So,
number of sides = sides per octagon × number of octagons
y = 8 × x
So the rule is y = 8x.
2.   Apply the rule
To apply the rule ( y = 8x), substitute the input values for x in the rule.
8   →
  8(8)  
→   64
3   →
  8(3)  
→   24
6   →
  8(6)  
→   48
2   →
   8(2)  
→   16
So the answer is
Rule:
Number of octagons (x)Number of sides (y)
8
3
6
2

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