INTRODUCTION..

Forming equations from words- Instruction/Examples

Algebraically solve real world problems!

For example…

We have a rectangle with sides 10cm and 6cm and need to create a box. To do this we need to cut a square out of each corner to fold into a box. Make a equation to model the volume of the box.

Drawing the problem out

How?

1. Automatically we know to get the volume of a cube is side x side x side.

2. So we need to remove 2x’s(the corners) from the sides to make up the height of the cube (6-2X’s) and (10- 2X’s) and X. X being the height of the new box.

The Result

We can plug in the sides in the normal volume of a cube equation to get the maximum and minimum volumes for our cube folded from our 2D 6x10 box.

So x(6-2x)(10-2x) is our equation for the cube. Congratulations!

1 More!

Find the area of a rectangle whose length is 5 more than its width.

GO!

The Result

x(x+5)

What did you get?

Try and model a function from this problem…

Jimmy Bieber, Justin Bieber’s second-best brother was traveling an average of 57 miles per hour on a 978 mile trip. How long did this trip take?

The Answer

17.157 hours. We get this by… 978 miles/57 mph=17.157 hours How many minutes is this?

› 17.157 hours/60 minutes in one hour This is 1029.47 minutes or 17 hours

and 9 minutes.

And don’t forget to do the Assessment!

Are there any questions on this lesson?

Citation

Demana, Franklin D., Bert K. Waits, Gregory D. Foley, and Daniel Kennedy. Precalculus Book. 8th ed. N.p.: Addison-Wesley, n.d. Print.

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