geno3141

Let x = number of students who got 100

Let y = number of students who got 90

Let z = number of students who got 80   --->   z = 20

Number of students:

      x + y + z = 48   --->   x + y = 28   (since z = 20)

Points:  100x + 90y + 80z  =  48(90)              (since the average for 48 students was 90 points each)

            100x + 90y + 80(20)  =  4320

            100x + 90y  =  2720

Putting these two equation together:  

      x    + y  =  28   --->     (multiply by 90)     --->     90x + 90z  =  2520

100x + 90y  =  2720   --->     (change signs)   --->    -100x - 90y  =  -2720

Adding down the columns:                                          -10x         =  -200

                                                                                          x   =  20

Since x + y  =  28   --->  y = 8

Questions 1 and 2 seem to be the same question. Using the method of successive subtractions, you can show that it can't be linear, quadratic, nor cubic. However, because of the missing value for x = 6, I can't take it past that. Perhaps someone else can.

Question 3: Place the data for year into L1 and the data for median age into L2, and check LinReg, QuadREg, CubicReg, and QuartReg, until you get one of the answers listed. (None are perfectly close, just match the possible answer to what your calculator gave you.

Question 4: Use your answer of Question 3 to solve this question.

Question 5 is like Question 3.

Question 6: Place the data for year into L1 and the data for percentage into L2, and check LinReg, QuadREg, CubicReg, and QuartReg, until you get the highest R-value. Choose that for the formula you will use to get the answer.

a) 15 min = 15 min x 60 s/min  =  900 secs

    300 000 x 900  =  270 000 000 km  =  2.7 x 10^8 km

b) 1 hour = 60 min/hr x 60 s/min  = 3600 secs  

     300 000 x 3600  =  1 080 000 000 km  =  1.08 x 10^9 km

c) 24 hours = last answer times 24

d) 1 year = last answer times 365 (approximately; go on-line for a better approximation)

You can get a decimal approximation from the calculator:  .36585 36585 36585 ...

Working it as common fractions:  3 3/4  =  15/4               10.25  =  10 1/4  =  41/4

     15/4 ÷ 41/4  =  15/4 x 4/41  =  15/41

Assuming that AD is the distance from A to D and CD is the distance from C to D, you'll need to tell me something about the position of B.

Do you mean the "mean-value theorem"?

To increase something by 10%, you can multiply by 1.10 (The 1 give you back the original amount, the .10 give the extra 10%).

To increase something by 12%, you can multiply by 1.12 (The 1 give you back the original amoun,t the .12 give the extra 12%).

To decrease something by 4%, you can multiply by 0.96 (0.96 = 1.00 - 0.04; the 1 gives you back the original amount, the -0.04 decreases that amount by 4%).

Let's say that the original amount was $100.00.

After a 10% increase:  $100.00 x 1.10  =  $110.00.

Starting with $110.00, after a 12% increase:  $110.00 x 1.12  =  $123.20.

After a 4% decrease:  $123.20 x 0.96  =  $118.272.

I don't understand the phrase "percentage of variation in prices in those three years"; could it mean that they are looking for the final percent of variation after three years? If so, it would be 18.272%. (And that's why I started with $100.00.)

Need to translate 8 into a fraction that has 7ths:  8  =  7 + 1  =  7 + 7/7

7 + 7/7 - 6/7  =  7 + 1/7  =  7 1/7

You can use the on-line calculator at this site to find that answer.

Would you like to know how to find the answer without using a calculator?

1)  Find the amount of change.

2)  Divide by the original amount.

3)  Multiply that answer by 100.

Example: What is the percent of change of something that started at 324 and ended at 402?

1)  Amount of change:  402 - 324  =  78

2)  Divide that answer by the original number:  78 / 324  =  0.241 (approximately)

3)  Multiply that answer by 100:  0.241 x 100 = 24.1%