Friday, October 1st, 2010
Solution:
- Let m = the number of men (an integer)
- Let w = the number of women (an integer)
- Let c = the number of children (an integer)
- Number of bushels = 3m+2w+.5c = 100
- Number of people = m+w+c=100
- 0<m<100
- 0<w<100
- 0<c<100
If we assume that there are 10 children, then we can solve for two equations and two unknowns:
- 3m+2w+5 = 100
- m+w+10=100
We can solve this by subtracting two times the second equation from the first equation:
- 3m+2w+5 = 100
- 2m+2w+20=200 (this is two times the second equation shown above)
- m – 15 = -100 (this is the result of subtracting two times the second equation from the first equation)
- m = -85
- w=100-10- (-85) = 175
The problem with this result is that the values for m and w are outside the allowable range, so clearly the assumption that there are 10 children is wrong. Let’s try increasing the number of children to 80 and see how that impacts the result from m:
- 3m+2w+40 = 100
- 2m+2w+160=200
- m -125 = -100
- m = 25
- w = 100-80-25=-5
Here, the result for m is within the range, but the value for w is outside the range. Let’s try reducing the number of children to 70:
- 3m+2w+35 = 100
- 2m+2w+140=200
- m -105 = -100
- m = 5
- w = 100-70-5= 25
Now we have a solution that makes sense (m=5, w=25, c=70). However, there may be other answers that work, so let’s try increasing the number of students to 72 and see what happens:
- 3m+2w+36 = 100
- 2m+2w+142=200
- m -106 = -100
- m = 6
- w = 100-72-6= 22
This solution also makes sense (m=6, w=22, c=72). Clearly, there can be several correct solutions to this question.
Friday, October 1st, 2010
Solution:
- Notice that 444 * 111 = 4*111*111
- The square root of 4 is 2
- The square root of 111*111 is 111
- So the square root of 4*111*111 = 2*111
- The answer is therefore 222
Friday, October 1st, 2010
Solution:
Base ten blocks are a mathematical manipulative used to learn basic mathematical concepts including addition, subtraction, number sense, place value and counting. You can manipulate the blocks in different ways to express numbers and patterns. Generally, the 3-dimensional blocks are made of a solid material such as plastic or wood and come in four sizes to indicate their individual place value: Units (one’s place), Longs (ten’s place), Flats (hundred’s place) and Big Blocks (thousand’s place). There are also computer programs available that simulate base ten blocks.
Since the number that is being modeled has a zero in the tens place and a zero in the ones place, there are no Longs or Units. Since the number is less than 999, there are no Big Blocks. That leaves only Flats, and there must be five Flats. Since each Flat represents one hundred, the number must be 500.
Friday, October 1st, 2010
Solution:
- There are seven days in a week
- If there are 7 students, they could all have been born on different days of the week
- If there are 8 students, we could guarantee that 2 of them were born on the same day
- If there are 15 students, we could guarantee that 3 of them were born on the same day
- F there are 22 students, we could guarantee that 4 of them were born on the same day
Friday, October 1st, 2010
Solution:
- If you have 26 choices for each letter in a word, then there are 26 such one-letter words, 262 two-letter words, 263 three-letter words, etc. There would be 268 eight-letter words.
- There would be 267 eight-letter words that end with the letter N, which is the same as the number of 7 letter words (just add “N” to the end of each seven-letter word.
- There would be 266 eight-letter words that begin with R and end with N (just add R to the front and N to the end of all six-letter words.
- There would be 2*267 eight-letter words that begin with an A or B (add A to the beginning of every seven-letter word, then add B to the beginning of every seven-letter word).
- There would be 2*267 eight-letter words that begin with A or end with B (add A to the beginning of every seven-letter word, then add B to the end of every 7 letter word).
Friday, October 1st, 2010
Solution:
Each ordered paid represents x and y: (x,y)
To calculate y, you can plug in x.
If y=3x-1, then the given values of x will result in the pairs (0,-1) (2,5) (-1,-4).
If y=3-2x, then the given values of x will result in the pairs (-1,5) (0,3) (1,1).
If y=2x+1, then the given values of x will result in the pairs (0,1) (-1,-1) (1,3).
Friday, July 23rd, 2010
Solution:
1. The cardinality of a set is a measure of the “number of elements of the set”. For example, the set A = {2, 4, 6} contains = elements, and therefore A has a cardinality of 3.
2. Given a set S, the power set of S, written , P(S), is the set of all subsets of S, including the empty set and S itself.
3. If S={a, b}, then P(S) ={{},{a},{b},{a,b}} and the Cardinality of P(S) is 4.