Question

functions, part 1 a function is a set of number pairs that contain a rule. we will be finding or following number pairs. we study pairs of numbers to determine the rule for the function. then we use the rule to find the missing number. note that for a function there is exactly one \out\ number for every \in\ number.
example 2 find the missing number.
solution we study each \in - out\ number pair to determine the rule of the function. we see that for each complete pair, if the \in\ number is multiplied by 3, it equals the \out\ number. so the rule of the function is \multiply by 3.\ we use this rule to find the missing number. we multiply 7 by 3 and find that the missing number is 21.
practice
a. copy this rectangle on your paper and show its lines of symmetry.
b. the y - axis is a line of symmetry for a triangle. the coordinates of two of its vertices are (0, 1) and (3, 4). what are the coordinates of the third vertex?
find the missing number in each diagram.
c.

in	function	out
3		15
7		□
9		45

d.

in	function	out
1		□
3		7
5		9

1. it is 1.4 kilometers from jim’s house to school. how far does jim walk going to and from school every day for 5 days?
2. the parking lot charges 75¢ for each half hour or part of a half hour. if edie parks her car in the lot from 10:00 a.m. until 1:05 p.m., how much money will she pay?

Explanation:

Step1: Identify rule for part c

Observe pairs: $4 \times 5 = 20$, $3 \times 5 = 15$, $9 \times 5 = 45$. Rule: multiply by 5.

Step2: Calculate part c missing value

$7 \times 5 = 35$

Step3: Identify rule for part d

Observe pairs: $0 + 4 = 4$, $3 + 4 = 7$, $5 + 4 = 9$. Rule: add 4.

Step4: Calculate part d missing value

$1 + 4 = 5$

Step5: Solve symmetry part b

For y-axis symmetry, $(x,y) \to (-x,y)$. So $(3,4) \to (-3,4)$

Step6: Solve rectangle symmetry part a

A rectangle has 2 lines of symmetry: 1 horizontal (midpoint of top/bottom sides) and 1 vertical (midpoint of left/right sides).

Answer:

a. The rectangle has 2 lines of symmetry: one vertical line through the midpoints of the left and right sides, and one horizontal line through the midpoints of the top and bottom sides.
b. $(-3, 4)$
c. 35
d. 5