WRITING AN EQUATION FROM A DESCRIPTION
About "Writing an equation from a description"
Writing an equation from a description :
We can use information from a description of a linear relationship to find the slope and y-intercept and to write an equation.
Writing an equation from a description - Examples
Example 1 :
The rent charged for space in an office building is a linear relationship related to the size of the space rented.At west main street office rentals, $750 rent charged for 600 square feet of space and $1150 rent charged for 900 square feet of space. Write an equation in slope-intercept form for the rent at West Main Street Office Rentals.
Solution :
Step 1 :
Identify the independent and dependent variables.
The independent variable (x) is the square footage of floor space.
The dependent variable (y) is the monthly rent.
Step 2 :
Write the information given in the problem as ordered pairs.
The rent for 600 square feet of floor space is $750 :
(600, 750)
The rent for 900 square feet of floor space is $1150 :
(900, 1150)
Step 3 :
Find the slope.
m = (y₂ - y₁) / (x₂ - x₁)
Substitute (600, 750) for (x₁, y₁) and (900, 1150) for (x₂, y₂).
m = (1150 - 750) / (900 - 600)
m = 400 / 300
m = 4/3
Step 4 :
Find the y-intercept.
Use the slope 4/3 and one of the ordered pairs (600, 750).
Slope-intercept form :
y = mx + b
Plug m = 4/3, x = 600 and y = 750.
750 = (4/3)(600) + b
750 = (4)(200) + b
750 = 800 + b
-50 = b
Step 5 :
Substitute the slope and y-intercept.
Slope-intercept form
y = mx + b
Plug m = 4/3 and b = -50
y = (4/3)x + (-50)
y = (4/3)x - 50
Example 2 :
Hari’s weekly allowance varies depending on the number of chores he does. He received $16 in allowance the week he did 12 chores, and $14 in allowance the week he did 8 chores. Write an equation for his allowance in slope-intercept form.
Solution :
Step 1 :
Identify the independent and dependent variables.
The independent variable (x) is number of chores Hari does per week
The dependent variable (y) is the allowance he receives per week.
Step 2 :
Write the information given in the problem as ordered pairs.
For 12 chores, he receives $16 allowance :
(12, 16)
For 8 chores, he receives $14 allowance :
(8, 14)
Step 3 :
Find the slope.
m = (y₂ - y₁) / (x₂ - x₁)
Substitute (12, 16) for (x₁, y₁) and (8, 14) for (x₂, y₂).
m = (14 - 16) / (8 - 12)
m = (-2) / (-4)
m = 1/2
m = 0.5
Step 4 :
Find the y-intercept.
Use the slope 0.5 and one of the ordered pairs (8, 14).
Slope-intercept form :
y = mx + b
Plug m = 0.5, x = 8 and y = 14.
14 = (0.5)(8) + b
14 = 4 + b
10 = b
Step 5 :
Substitute the slope and y-intercept.
Slope-intercept form
y = mx + b
Plug m = 0.5 and b = 10
y = 0.5x + 10
After having gone through the stuff given above, we hope that the students would have understood "Writing an equation from a description".
Apart from the stuff given above, if you want to know more about "Writing an equation from a description", please click here
Apart from the stuff given in this section, if you need any other stuff in math, please use our google custom search here.
WORD PROBLEMS
HCF and LCM word problems
Word problems on simple equations
Word problems on linear equations
Word problems on quadratic equations
Area and perimeter word problems
Word problems on direct variation and inverse variation
Word problems on comparing rates
Converting customary units word problems
Converting metric units word problems
Word problems on simple interest
Word problems on compound interest
Word problems on types of angles
Complementary and supplementary angles word problems
Markup and markdown word problems
Word problems on mixed fractrions
One step equation word problems
Linear inequalities word problems
Ratio and proportion word problems
Word problems on sets and venn diagrams
Pythagorean theorem word problems
Percent of a number word problems
Word problems on constant speed
Word problems on average speed
Word problems on sum of the angles of a triangle is 180 degree
OTHER TOPICS
Time, speed and distance shortcuts
Ratio and proportion shortcuts
Domain and range of rational functions
Domain and range of rational functions with holes
Graphing rational functions with holes
Converting repeating decimals in to fractions
Decimal representation of rational numbers
Finding square root using long division
L.C.M method to solve time and work problems
Translating the word problems in to algebraic expressions
Remainder when 2 power 256 is divided by 17
Remainder when 17 power 23 is divided by 16
Sum of all three digit numbers divisible by 6
Sum of all three digit numbers divisible by 7
Sum of all three digit numbers divisible by 8
Sum of all three digit numbers formed using 1, 3, 4
Sum of all three four digit numbers formed with non zero digits
