Solving inequalities: how many trips needed so sticker costs

K

kilrif

New member
Joined
Sep 6, 2008
Messages
4
OK...My 11th grade daughter and I need HELP with guidance in setting up Inequality Word Problems...is there any software you recommend or websites specific to Alegebra II help that give good, clear examples?? Her teacher is doing poorly at giving examples and is now on trimesters for the first time in the school's history and this is a nightmare for her and me.

Here is one example...

Toll charge is 50 cents. If you purchae the special sticker it is $5.50 (one time cost) and 35 cents then each toll thereafter ...How many trips are needed into tunnel before the sticker costs less than paying per trip separately?

50t > 550 + 35t
15t> 550
t> 36.6

Does this seem correct??????????
 
Re: Solving inequality word problems...HELP

correct ... all that is left is to interpret the desired solution from the last inequality, t > 36.7, remembering that t is a whole number.
 
Re: Solving inequality word problems...HELP

Looks good to me. May I make three suggestions that will sound like nit-picking but will help in the long-run if adopted.

1) Name things to start. Take the time to write it/them out in long hand. For this problem, I would suggest "Let t represent the number of trips." This really helps when you have other types of problems where things are easily confused. For instance, in a coin problem don't write "d=dimes." Make it specific like "d = the number of dimes" or "d = the value of the dimes." There is a difference.

2) In this problem it makes no difference in that the number of trips is greater than 36 2/3. If it were an equality rather than an inequality, is there any such thing as 2/3 of a trip? You would probably have to decide whether the answer was equal to 36 trips or 37 trips. Minor detail.

3) Round off correctly. Your answer of 36.6 is not correct technically. 36 2/3 expressed as a decimal rounded to one decimal place is 36.7; rounded to two decimal places is 36.67; etc. Sometimes it is better to express the answer as a common fraction or mixed number rather than a decimal fraction.

If you need more help, don't hesitate to ask. Keep up the good work.
 
Re: Solving inequality word problems...HELP

Another way is simply equate them:
5.50 + .35t = .50t
550 + 35t = 50t (not a requirement, but usually easier is you get rid of decimals)
15t = 550
t = 36 2/3

So 37 trips is the "magic" point.
 
You must log in or register to reply here.
Top