Money spent + money left over = total money
money spent + 9 = 30
We don't know the price of each shirt, so let x = price of 1 shirt.
Then, 3 shirts cost 3 times as much as x, or 3x.
She spent 3x.
3x + 9 = 30
Well, we could try adding up odd numbers, and look to see when we reach 400. But I'm hoping to find an easier way.
First of all ... I'm not sure this will help, but let's stop and notice it anyway ...
An odd number of odd numbers (like 1, 3, 5) add up to an odd number, but
an even number of odd numbers (like 1,3,5,7) add up to an even number.
So if the sum is going to be exactly 400, then there will have to be an even
number of items in the set.
Now, let's put down an even number of odd numbers to work with,and see
what we can notice about them:
1, 3, 5, 7, 9, 11, 13, 15 .
Number of items in the set . . . 8
Sum of all the items in the set . . . 64
Hmmm. That's interesting. 64 happens to be the square of 8 .
Do you think that might be all there is to it ?
Let's check it out:
Even-numbered lists of odd numbers:
1, 3 Items = 2, Sum = 4
1, 3, 5, 7 Items = 4, Sum = 16
1, 3, 5, 7, 9, 11 Items = 6, Sum = 36
1, 3, 5, 7, 9, 11, 13, 15 . . Items = 8, Sum = 64 .
Amazing ! The sum is always the square of the number of items in the set !
For a sum of 400 ... which just happens to be the square of 20,
we just need the <em><u>first 20 consecutive odd numbers</u></em>.
I slogged through it on my calculator, and it's true.
I never knew this before. It seems to be something valuable
to keep in my tool-box (and cherish always).
Answer:
Step-by-step explanation:
1. USING MULTIPLICATION
FIRST 2\times 9=18
SECOND 2\TIMES 8=16
THIRD 9\TIMES 9=81
FOURTH 9\TIMES 8=72
Answer: There are two solutions and they are
theta = 135
theta = 225
=============================================================
Explanation:
Recall that x = cos(theta). Since the given cosine value is negative, this indicates x < 0. Theta is somewhere to the left of the y axis, placing it in quadrant 2 or quadrant 3.
It turns out there are two solutions, with one solution per quadrant mentioned above. Use the unit circle to find that the two solutions are:
theta = 135
theta = 225
You're looking for points on the unit circle that have x coordinate equal to x = -sqrt(2)/2. Those two points correspond to the angles of 135 and 225, which are in quadrants 2 and 3 respectively.
--------
I recommend using your calculator to note that
-sqrt(2)/2 = -0.70710678
cos(135) = -0.70710678
cos(225) = -0.70710678
The decimal values are approximate. Make sure your calculator is in degree mode. Because those three results are the same decimal approximation, this indicates that cos(135) = cos(225) = -sqrt(2)/2.
Answer:
1. you start with $ 3 and save $1 each month
2. your total savings is 3 times the number of month multiplied by itself
3. you save $3 the first month and then each month the amount triples
Step-by-step explanation:
1.
as y axis represents savings while x axis represents months
the statement "you start with $ 3 and save $1 each month"
is best described by the graph of straight line having slope of 1 and intercept of 3.
2. your total savings is 3 times the number of month multiplied by itself
= 3(x)(x)
= 3x^2
3. as y axis represents savings while x axis represents months
the statement "you save $3 the first month and then each month the amount triples" is best described by the exponential graph starting to rise from point (1,3) which means $3 save at 1 month.
!
