Questions

[calcguy1350]

I have questions on the proportions and regressions.

12B-46 A bucket is filled with 139 50-mm stones. How many 7-mm pebbles would it take to fill the bucket? Answer: 50700

12B-47 Freda reads a book a little bit each day. After some time, she started keeping track of the daily starting page numbers: 154, 176, 194, 209, 239. Estimate how long it would take to read the entire book if it is 421 pages long. Answer: 20.7days.

[Shawn]

46) [unparseable or potentially dangerous latex formula]
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47) Data:
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Use HP or however you do linear regression (I recommend HP) to find m, which is the slope, which is 20.3. (Let me know if you don't know how to do linear regression period, but your post sounded like you do)
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This is number of pages divided by "best fit" amount per day to get days to read.

[calcguy1350]

Thanks!
Do you know how to do these also?
12A-27 Quincy bikes 4mi to school in 15min and walks to school in 65 min. She biked a distance d one day towards school and had a flat tie. She walked the rest of the way. What is d if her total time to school was 33min? Answer: 2.56mi

12A-28 Daria has 25 coins totaling $2.41. She has twice as many dimes as pennies, and one less nickel than quarters. How many nickels and dimes does she have?
Answer: 15 integer

[calcguy1350]

My calculators are Ti-89 and HP-33sII if that helps so that you can explain me better.

[Shawn]

Of course I do.
27)
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Then set up combined rates:
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Equation Solver
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28) System of Equations
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Substitute 1st
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Substitute 2nd
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Solve however you like
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[Shawn]

[calcguy1350]

2 more questions:

How do you edit matrices in the home menu? Does that mean that you input the matrix in the home menu, or you still have to go to the matrix editor in the apps?

Another proportion:
12D-46 The specific surface area S of a particle is its total surface area divided by its mass. If a 200 micron sized particle had S=1m^2/g, what size particle identical shape has S=50m^2/g? Answer: 4.00

[nsguy1350]

[Shawn]

rref would be quicker. Go to matrix find rref then enter the matrix. To do this enter the matrix in this form.
[[a,b,c][d,e,f]], using brackets to seperate rows and commas elements in rows. For example to solve the system
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I would simply type in the homescreen:
rref([[3,2,26][21,30,246]]), which would return a matrix with 0's and 1's in the first two columns and the solution in the 3rd. With the left variable showing up at the top in the first row and right variable in the second row. Any method of solving the system works, though the key is knowing how to set it up.

[redhawk2015]

Also from Invitational A, can anyone help me with Numbers 36, 38, and 39?

[Shawn]

12D-46) This proportion problem doesn't make sense to me. The scaling should be 2/3, I would think, but it is linear. If someone could explain this I would appreicate it.
The key to the problem is relealzing that as something gets larger the surface area to volume ratio gets smaller. This makes it an inverse relationship (flip one the top/bottom of the scaling fractation.)
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[Shawn]

Also, 36,38,39. I hope it is 12A and not some other test:
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I don't do sig figs:
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Rounds to key

[Shawn]

38) Prevent the problem by knowing the difference between tea and table spoons....
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First concentration wrong:
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Desired concentration:
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You want to 1/3 the concentration so get rid of 2/3
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So dump out 2/3 of a gallon
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[Shawn]

39) My method would take too long, look in the manual for the formula that works or search circle/triangle here for it.