Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.



Re: Word Problem help
Posted:
Apr 17, 2004 12:34 PM


jacqueline wrote: > i ahve a few word problems that are getting to me.... my sister had > them and she doesnt remember the answers they were from her class. if > you could help it would be great
You'll never learn how to do math by copying someone else's answers.
> here are a few of teh questions.... > 1. 2 pumps can fill a pool in 4 and 5 hrs respectively. at noon the > slower one is turned on and at 1"00 the other is started. at what time > will the pool be filled.
After one hour, what fraction of the pool has the slow pump filled? (Hint: It can fill 5/5 of the pool in 5 hours)
In another hour, what fraction of the pool has the slow pump filled? (Hint: It can fill 4/4 of the pool in 4 hours)
The fast pump has been on for an hour, what fraction of the pool does it fill in one hour?
What is the total fraction filled by 2:00?
In another hour how much will the slow pump fill? The fast pump?
How much of the pool is filled?
> 2. how many 6 digits palindromic numbers are there?
A palindromic number is a number in the form abccba, where the a, b and c each stand for one digit (a palindrome is something that reads the same backwards as it does forwards). Does that help? Try picking numbers and see if you can see a pattern.
> 3. of 75 students surveyed: 48 like basketball,45 like footbal,58 like > baseball,28 like basket and foot,37 like foot and base, 40 like basket > and base,and 25 like all 3 > how many like only baseball, and how many dont like any?
This is a fun type of problem to solve. Draw three circles that all overlap. Like this:
/\ /\ / \ / \ / \/ \ / /\ \ / / \ \ / / \ \ / Basketball / b \ Football \ / /\ \  a /   \ c   /   \   /  d  \  \  \ /  / \  \ /  / \  e \ / f  / \  \/  / \  /\  / \/ \/    Baseball  \ / \ g / \/
Now start filling in the circles from the middle out. 25 like all 3, so put the number 25 in the section labeled d, where all three circles overlap. Those 25 students like all 3, so they are in all three circles. There are 37 who like football and baseball, so the total number of students in sections d & f is 37. Fill in f. There are 28 who like basketball and football, that means sections b & d. So fill in b. There are 40 who like baseball and basketball, which are sections d & e. So fill in e. The 48 students who like basketball fill the basketball circle. You should be able to fill in section a. You can now fill in sections c & g the same way. Those who like only baseball are in section g. If you add up all the sections you'll find out how many like any of those sports. The total number of students is 75, so you can figure out how many don't like any.
I think this is a cool way to figure out problems like this, it is called a Venn diagram.
> 4. the thickness of a piece of cardboardcan be doubled by folding it > over. how many times would you have to fold the piece over before > the thickness would reach the moon?
That's a good question. Do you know how far it is to the moon? You can look that up. What about the thickness of a piece of cardboard? If you use the measurements in kilometers to the moon and milimeters for a piece of cardboard things will be easier. There are 1,000 milimeters in one meter and there are 1,000 meters in one kilometer. So there are 1,000 x 1,000 or 1,000,000 milimeters in a kilometer. So if you multiply the number of kilometers to the moon by one million and then divide by the thickness of a piece of cardboard you can find out how many thicknesses of cardboard you need to reach the moon. Say you already folded a piece of cardboard to that thickness, if you unfolded it one time how thick would the cardboard be? Keep unfolding the cardboard and counting until you are down to 1 or less. You've now counted the number of folds you needed to make to reach the moon.
Jeff
 A man, a plan, a cat, a canal  Panama!
Those who do not learn from history are doomed to repeat it. George Santayana
Unthinking respect for authority is the greatest enemy of truth. Albert Einstein
 submissions: post to k12.ed.math or email to k12math@k12groups.org private email to the k12.ed.math moderator: kemmoderator@k12groups.org newsgroup website: http://www.thinkspot.net/k12math/ newsgroup charter: http://www.thinkspot.net/k12math/charter.html



