Trying to help child with systems of equations word problems and totally lost HELP !

[momneedshelp]

Jacob bought 8 pairs of pants for a total of $460. Dress pants cost $70 and jeans cost $20. How may of each type of pants did he buy?

must be solved using slope intercept form

 

[stapel]

Jacob bought 8 pairs of pants for a total of $460. Dress pants cost $70 and jeans cost $20. How may of each type of pants did he buy?

must be solved using slope intercept form

Trying to "speak" through an "interpreter" who doesn't "speak the language" has a very poor success ratio. It would be very helpful if we could communicate directly with the student. For a start:

The subject line refers to "systems of equations" but the post says that this "must be solved using slope intercept form". Which is correct?

When you reply, please include your work so far, starting from the basics, such as the variables you chose to represent the two unknowns. Thank you! :wink:

 

[Deleted member 4993]

Jacob bought 8 pairs of pants for a total of $460. Dress pants cost $70 and jeans cost $20. How may of each type of pants did he buy?

must be solved using slope intercept form

Let

the number of Jeans = J

the number of Dress-pants = D

Then ...bought 8 pairs of pants

J + D = 8...............................................(1)

and...for a total of $460. Dress pants cost $70 and jeans cost $20

70 * D + 20 * J = 460 ............................(2)

Convert (1) and (2) into slope-intercept form and solve for J and D.

 

[JeffM]

Jacob bought 8 pairs of pants for a total of $460. Dress pants cost $70 and jeans cost $20. How may of each type of pants did he buy?

must be solved using slope intercept form

I do not quite understand the instructions.

The basic way to do word problems is, first, to identify what must be found and to assign a unique letter to each item to be found.

d = number of dress pants bought.

j = number of jeans bought.

Next step is to use those letters to translate the conditions of the problem into mathematical form.

j + d = 8.

70d + 20j = 460.

This two-step process will work for almost every word problem. From this point on, the problem is just mathematical mechanics.

Hope this helps. By the way, it is probably best to have your child do each step on his or her own with your guidance where necessary. Doing is better than seeing.

Addition: I agree with stapel. Having the child communicate directly with us is likely to be more productive. We sometimes bark but we never bite.

 

[Kaylaemarx]

I suppose just solving for j and d will help us with the answer. I don't think we need slope intercept form to solve this.

 

[HallsofIvy]

I suppose just solving for j and d will help us with the answer. I don't think we need slope intercept form to solve this.

Yes, but if your grade depends upon following instructions and the instructions say "use the slope intercept form", you bow your head and use the slope intercept form!

As has already been said, the information given tells us that j + d = 8 and 70d + 20j = 460, with "j" the number of jeans bought and "d" the numbr of dress pants. Slope intercept form, in and xy- coordinate system, would be "y= mx+ b" where m is the slope and b is the y-intercept. Using "d" in place of "y" and "j" in place of "x", the slope intercept form for the first would be d= -j+ 8 and for the second, after first writing 70d= -20j+ 460, d= -(2/7)j+ (46/7).

Since both of those expressions are equal to d we can set them equal:
-j+ 8= -(2/7)j+ (46/7) and solve that equation for j.