Transcript Writing_Equations

Algebra 2
1.6
Pinkston
SAT Question
What is the greatest possible sum of three
consecutive even integers whose product is zero?
A.-6
Zero has to be one of the
B.-3
numbers, so the possibilities
C.0
are:
D.3
-4, -2, 0
E.6
-2, 0, 2
0, 2, 4
The one that gives the greatest
sum is the last one: sum is 6.
Solving Word Problems
In Algebra County
Write Heading
Write Equation
Solve Equation
Write Solution asked for
On Wednesday, Harry picked 3 times as many
quarts of berries as on Tuesday. On Thursday, he
picked 5 times as many quarts as on Tuesday. In
all he picked 153 quarts. Find the number he
picked each day.
The heading defines the variables
needed to solve the problem.
x is the variable we know the least
about.
On Wednesday, Harry picked 3 times as many
quarts of berries as on Tuesday. On Thursday, he
picked 5 times as many quarts as on Tuesday. In
all he picked 153 quarts. Find the number he
picked each day.
For this problem, we need to make
variables for:
Which one do
Tuesday x
we know the
Wednesday 3x
least about?
Thursday 5x
On Wednesday, Harry picked 3 times as many
quarts of berries as on Tuesday. On Thursday, he
picked 5 times as many quarts as on Tuesday. In
all he picked 153 quarts. Find the number he
picked each day.
“In all” means add up all the
variables for each day.
x  3x  5x  153
x  3x  5x  153
9 x  153
9
9
x  17
Now, go back to the heading to write
all the solutions asked for.
On Wednesday, Harry picked 3 times as many
quarts of berries as on Tuesday. On Thursday, he
picked 5 times as many quarts as on Tuesday. In
all he picked 153 quarts. Find the number he
picked each day.
For this problem, we need to make
variables for:
Tuesday x  17 quarts of berries
Wednesday 3x  3(17)  51 qts.
Thursday 5x  5(17)  85 qts.
Tuesday x  17 berries
Wednesday 3x  3(17)  51 berries
Thursday 5x  5(17)  85 berries
We can check it by adding
the three answers together
to see if we get 153.
Example 2
The time that a traffic light remains yellow is
1 second more than 0.05 times the speed
limit. What is the yellow time for a traffic
light on a street with a speed limit of 30
mi/h? Heading:
x = yellow time
y = speed limit
Equation:
x = 1+.05y (Substitute 30 for y)
x =1+.05(30)
Solve:
x =1+.05(30)
x = 2.5
Write solution:
2.5 sec.
Example 3
It has been found that the world record for the
men’s 10,000 meter run has been decreasing
steadily since 1950. The record is approx. 28.87
minutes minus .05 times the number of years
since 1950. Assume the record continues to
decrease in this way. Predict what it will be in
2010.
Heading:
x = world record
y = years since 1950
Equation:
x = 28.87 - .05y
Solve:
x = 28.87 - .05y
Substitute 60 for y
x = 25.87
Write solution:
25.87 min.
To find the percent of increase or decrease:
Amount of increase or decrease
Original number
Example 3:
16/p. 33.
In 1995 the average American ate 48.8 lb of chicken.
This was 6.3 lb more than the average in 1990.
What was the percent of increase in chicken
consumption from 1990 to 1995?
In 1990
??
Increase
In 1995
6.3
48.8
Amount of increase or decrease
Original number
48.8 – 6.3
6.3
42.5
=
14.8%
SAT Question
If x and y are negative integers,
which of the following must be
positive?
A. (-) + (-) is negative
A. x + y
B. (-) – (-) could be negative
or positive
B. x – y
C. Same as above
C. y – x
D. - [(-) - (-)] could be either
D. – (x – y) E. - [(-) + (-)] is definitely
E. – (x + y)
positive!
Classwork:
2, 8, 12, 16 / 33
Get ready for a “Small Quiz”
to be written
on your grade sheet.
Quiz. Copy the problems and write the
answer.
Solve and write answer in set notation:
5  3a  a 11
1.
2.
3
x  7
5
Put your grade paper on the front of
your row, quiz side down.
THE
END