Math Is Fun Forum

mathland

Member

Registered: 2021-03-25

Posts: 444

Sales

The slopes of lines representing annual sales y
in terms of time  x in years are given below. Use the
slopes to interpret any change in annual sales for a
one-year increase in time.

(a) The line has a slope of m = 135.
(b) The line has a slope of m = 0.
(c) The line has a slope of m = −40.

1. Must I use y = mxc+ b?

2. If not, what exactly is this question asking to do?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Sales

The wording is rather unclear.  I'm assuming that for a single year the line representing the increase (or decrease) is given by the value of m.

So in the first case, if the actual sales figure at the start was 100, then at the end it is 100 + 135/1 = 235.  So the percentage increase is (235-100)/100 %

If you use a different start value (not 100) , you'll find the result is the same.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathland

Member

Registered: 2021-03-25

Posts: 444

Re: Sales

The wording is rather unclear.  I'm assuming that for a single year the line representing the increase (or decrease) is given by the value of m.

So in the first case, if the actual sales figure at the start was 100, then at the end it is 100 + 135/1 = 235.  So the percentage increase is (235-100)/100 %

If you use a different start value (not 100) , you'll find the result is the same.

Bob

The answers in the back of the book are as follows:

(a) Sales increasing 135 units/yr
(b) No change in sales
(c) Sales decreasing 40 units/yr

Can you make sense of the answers related to the poor wording in the actual problem?

Last edited by mathland (2021-05-05 19:54:49)

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Sales

That fits with what I said.  First is 135% increase.

It takes longer to figure out what they're asking than to do it.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathland

Member

Registered: 2021-03-25

Posts: 444

Re: Sales

That fits with what I said.  First is 135% increase.

It takes longer to figure out what they're asking than to do it.

Bob

Ok. Strange problems. Who comes up with such questions?

Bob

Administrator

Registered: 2010-06-20

Posts: 10,140

Re: Sales

Yes, very strange and you're better off doing something more challenging I think

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

mathland

Member

Registered: 2021-03-25

Posts: 444

Re: Sales

Yes, very strange and you're better off doing something more challenging I think

Bob

You are right. I'm better off spending time learning real-life related problems normally taught in a classroom setting.