please help with a couple of math problems

[pookiepie]

1) what is the probability of six tails out of 9 tosses of a fair coin?

2) a candy store mixes jawbreakers worth 36 cents per pound with lollipops worth 52 cents per pound to make a 200 lb mixture worth 40 cents per pound. how many pounds of the lollipops did the store use?


..so much for higher level math classes

THANKS!

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[Balki]

Hey,

The first problem I remember doing here on SND several times you can use the search button or just look through the threads because there will be much more valuable information there. Click here for exact solution
http://forums.studentdoctor.net/showthread.php?s=&threadid=81368

Second Problem: Personally I love solving math problems with equations but this one is so much simplier to back solve. Take an answer( start with C) and plug it in. For example let's assume you try then answer of 100 pounds of Lolips (man that's a lot of candy) Tha leaves 100 pounds of the other candy. So in order for this to be true you must have
100*36+100*52)/200 = 40
But the answer of the right side is not 40 but is 44 so that is not the answer. From here you also are able to educately geuss what answer you should try next.
I am sure there is a way how to solve this using an equation, you can probably try, but time is precious and choosing numbers with percent problems and backsolving with age and candy problems might save you few minutes.
I hope this helps

-Balki-

 

[croco]

um..ya, if you have a college algebra book, look at the chapter on probability, it really explain equation that are used well

 

[jjflynn2]

The answer probably will be a 'nice' answer (like 100:100, 2/3:1/3, 75%:25%) so guess&try would probably work well. If you want to calculate, it's not that hard...

You are looking for the avg price of 200# to be .40/lb:
.36 J + .52 L = .40 J=lbs jawbreakers, L=lbs lollypops
---------------
200

Remember the rule, that when you have 2 Letters/Variables, you want to reduce it to one.

Let's get rid of J by putting it in terms of L:
J + L = 200 (given in problem)
J = 200 - L

So rewrite with one variable
.36 (200 - L) + .52L = .40
------------------------
200

start reducing:
a. get rid of the 200 denominator
.36 (200 - L) + .52L = 80

b. expand the parens
72 - .36L + .52L = 80

c. solve for L
.16L = 8 so L = 8/.16 L = 50

d. solve for J
J = 200 - L J = 150

We have 50# of lollypops and 150# of jbreakers

So if your first guess was 100L:100J giving you 44
and your second guess was 50L:150J giving you 40,
you saved some time by reasonably guessing. Otherwise, it's not that hard to compute. Keep practicing.