Math Central - mathcentral.uregina.ca
Quandaries & Queries
Q & Q
 Topic: model
start over

24 items are filed under this topic.

 Page1/1
A model of the sun and the Earth 2014-06-14
From Lynn:
There is a model of the sun that is 2 1/2 inches in diameter. This is the only clue we have! How far away is the earth from this model?
The spread of a rumor 2012-04-09
From Roohi:
The function f(t) = a/(1+3e^(-bt)) has also been used to model the spread of a rumor. Suppose that a= 70 and b=3 0.2. Compute f(2), the percentage of the population that has heard the rumor after 2 hours. Compute f'(2) and describe what it represents. Compute lim t approaches infinity and describe what it represents.
Sales as a function of advertising 2010-12-08
The sales S(in thousands if units) of a product after x hundred dollars is spent on advertising is given by S=10(1-e^kx). Find S as a function of x if 2500 units are sold when \$500 is spent on advertising.
A linear relationship 2010-06-22
From Laura:
The monthly cost of driving a car depends on the number of miles driven. Lynn found that in May it cost her \$300 to drive 480 miles and in June it cost her \$460 to drive 800 miles.

Question: Express the monthly cost C as a function of the distance driven d, assuming that a linear relationship gives a suitable model.

A scale model of a city 2010-05-18
From Briana:
Well I have to create a three dimensional city for a geometry project and it requires us to use precise scal factor and well we want to build a medium sized city but our teacher said that If we make or buildings to high our houses would look like super small compared to the tall building were trying to figure out if we were to build a medium sized city what scale factor should we use to make the houses big enough to see and design?
Answered by Walter Whiteley and Tyler Wood.
Modelling an underpass 2010-05-11
From Sue:
An engineer at the Ministry of Transport is creating the plans for a new road. This road will cross the path of a busy railway track so it will be necessary to built an underpass for this road. This underpass will be in the shape of a parabolic arch.

The specifications include:
-the road must be at least 10 m wide and it must have shoulders at least 2 m wide on either side of the road.
-there must be a clearance of 3 m over all areas of the road.

What quadratic equation could you use to model this bridge.

A model for the population of a Canadian city 2010-04-07
From jess:
Let t^2 represent t-squared. The population of a Canadian City is modelled by: f(t) = 12t^2 + 800t + 40,000, where t is the time in years. When t= 0, the year is 2007.
a) According to the model, what will the population be in 2010?
B) In what year is the population predicted to be 300,000?

A linear relationship 2010-02-24
From Mel:
This table shows the linear relationship between an aeroplane's height (above sea level) and the outside air temperature.
 h (cm) 120 340 480 600 1040 T (degrees C) 14.28 12.96 12.12 11.4 8.76
Find the gradient and vertical intercept of the function. Write the formula for T.

A 3D cardboard cupcake 2010-01-30
From Margaret:
Hi,
I'm an art student and I'm attempting to build a 3D cupcake out of cardboard. I want it to have a circular base of 8.5 inches and sides that are 7'' tall and slope outward so the top of the base is 29'. The top with the frosting would be a detachable lid made from a cone with a base circumfrance of 29". My problem is how to cut the side so they will slope out, I'm pretty sure there needs to be a curve, however I don't how to calculate the degree of it. Ideally I want the sides to be a single piece of cardboard. I also don't know how to calculate the arc needed to make a cone who's circular base's circumfrence is 29''.
Thanks,
Margaret

Constructing a scale model 2009-09-27
From Colleen:
What is the formula i need to use to find out how to state a reasonable scale in the question below; Suppose you were constructing a model that must sit on a piece of cardboard that is 22cm by 28cm. STATE THE REASONABLE SCALE that you can use to build a model to represent the following items. Determine the dimensions of the model.

a) a rectangular prism with a length of 5m and a width of 2m?

Fitting the curve y=a*exp(b*x)+c 2009-08-12
From aika:
Could one show me the complete algorithm and formula for finding the coefficients (a,b, and c) in exponential regression model y=a*exp(b*x)+c
Math in everyday life 2009-08-03
From Naveen:
Dear sir, We are advised to do a project on "Mathematical modeling to solve various problems of our everyday life/environmental related problems...... Can u plz help us by mailng some ideas, suggestion,reference to make my project successful.... Thanking you...... Waiting for your favourable reply......
The scale for a model train 2009-03-13
From Shelly:
Lindy is planning to build a model of a train using a scale where 2 inches represents 25ft. If the train is 60 feet long, what is the length in inches that Lindy should build the model of the train?
Answered by Stephen La Rocque and Penny Nom.
A linear model 2008-05-09
From Shelby:
How would you write a linear model to represent the population of a city that has a population of 547,725 and a growth rate of -25,195 per year with t represents the number of years since 1994?
A model for a building 2007-07-17
From Carl:
A model for a building is 50 centimeters long, 38 centimeters wide, and 225 centimeters tall on model 1 centimeter represents 2.5 meters. I need to find the volume of the actual building in cubic meters,and the surface area of the building including ceilings and floors. round to the nearest tenth of a square meter.
A scale model 2006-11-30
1) A model of a storage compartment is to a scale of 1:40. If the surface area of the model is 25 square centimeters, what is the surface area of the actual storage compartment?

a) The storage compartment in the last question has an actual volume of 8 cubic metres. What is the volume of the model?

A scale factor 2006-03-25
From Jackie:
I need a formula or step by step help to show my child how to find missing dimensions for example: The scale factor for a model is 10 inches = ________ feet
Model 39.7 in
Actual 11.9 ft

A train model is created using a scale of 1:60 2006-01-01
From Jennifer:
An "n gauge " train model is created using a scale of 1:60. If an actual train engine, the "K-4" an early twentieth-century engine,is 45 feet long, what is the length of an "N gauge" model of the engine in inches?
Modelling monthly temperature with a cosine 2004-12-25
From Regis:
The average monthly temperature for a location in Ontario as a function of month number can be modelled using the equation y = a cos[k(t + b)] + d.
The best linear model 2001-07-29
From Rebeca:
I am a student (senior) summer hire working for Dept of the Army Resource Management. I've been assisting the Analyst in developing a model to predict training costs. The technique we used was simple linear regression. Now I've been asked for my opinion in choosing the best model I feel is better. I've chosen #1. Garrison Training but I want a second opinion before I give my choice. I've taken basic statistics last year in high school and will probably be taking more this year. Could you look over the information and give me a reason my choice would not be best? The dep variable-y, is Training costs in dolars per day.

ModelInd Variable- Xabrsy.x
1.Garrison Training126.310.9820.9055117.2
2.Local Training212.161.370.7937142.7
3.Man Rig Area116.382.470.6481175.6
4.Major Training346.124.670.7280167.2

Conservation, consumption and population growth 2001-06-04
From Steve:
I'm trying to quantify the relation between conservation/consumption and population growth. For instance let's consider California:

The 2000 census states that California's population grew from 29,760* in 4-1990 to 33,871 in 4-2000. I want to find r or rate of growth per year. Based on the exponential growth formula for population growth:
.
.
.

Toy bricks 2001-05-13
From Sarah:
A regular-sized brick weighs 4 kilograms. How much will a similar toy brick, made of the same material, but all of the same dimensions of which are four times smaller, weigh?

The 300-metre tall Eiffel tower is made of steel and weighs 8 000 000 kg. An exact replica, made of the same material, weighs 1 kg. How high is the replica

A model area 1999-12-15
From John Ost:
Hello, I am a college student taking an elementary math course I need if possible assistance to developing an area model 36 x 25 that shows each of the four separate partial products. I must know how to do the computation 36x25 showing each of the four partial products separately, and indicate how each corresponds to the drawing that is required of the area model.