OG 12th Problem Solving 216-230

Question 216 – “(1/2)^-3…..”
OG Explanation is fine.
Khan Academy Question 233 – 1.50

Question 217 – “In a certain game a large contained is filled with red yellow green….”
OG Explanation is fine.
Khan Academy 234 – 4.25

Question 218 – “If 2/(1+2/y)…..”
OG Explanation is fine.
235 Khan Academy  7:10

Question 219 – “If a, b, and c are consecutive positive integers and…..”
OG Explanation is fine. Alternatives: To start off, let’s think above 3 consecutive integers: 2, 3, 4 or 9, 10, 11
For choice I, intuitively the difference between c and a is 2. TRUE
For choice II, at least one of a, b, or c is even; therefore abc is even. TRUE
For choice III, any set of 3 consecutive integers will one number each with remainders of 0, 1, and 2 when divided by 3. The remainders sum up to 3 which is equivalent to a remainder of 0. TRUE

Khan Academy Question 236 – Begins at 8.10

Question 220 – “A part time employee whose hourly wage was increased by 25 percent….”
OG Explanation is fine; this is a fairly easier problem for being in the 220’s. You could also pick numbers for his wage and hours.
237 Khan Academy - 0.00

Question 221 – “Of the 200 students at College T majoring…”
OG Explanation is fine.
Khan 239 – 5.50

Question 222 – “If 5 – 6/x = x…”
OG Explanation is fine. This is a disguised quadratic.

Question 223 – “Seed mixture X is 40% rygrass…”
OG Explanation is okay. Alternatively, If the mixture X and Y contains 30% and X contains 40% and Y contains 25% then we need 2 parts of Y and 1 part of X (this is like a weighted average problem). Having 1 part X, 2 part Y means 1/3rd of the mixture of 33.3% is of mixture X.

Khan Question 240 Begins at 0.00
Question 224 – “If n is a positive integer…”
OG Explanation is fine.
Khan Question 242, 4.55

Question 225 – “A straight pipe 1 yard in length was marked off in fourths….”
OG Explanation is fine. This is actually a tricky problem.
Khan Question  243  begins at  6.30

Question 226 – “If 0.0015….”
OG Explanation is fine
Khan 244 – 9.00 (mislabeled as question 245 in video)

Question 227 – “If x + y = a and x – y = b…”
OG Explanation uses the Algebraic approach but I think that would be difficult to do in 2 minutes. I would just pick numbers. Let x = 3 and y = 5 2xy=2(3)(5)=30. a = x + y = 8 and b = x – y = -2

Choice A: (64-4)/2 = 30 CORRECT
Choice B: (4 – 64)/2 = – 30 INCORRECT
Choice C: (8- -2)/2 = 10/2 = 5 INCORRECT
Choice D: (8)(-2)/2 = -8 INCORRECT
Choice E: (64 + 4)/2=68/2=34 INCORRECT

245 Khan Academy Begins at 0.00

Question 228 – “An arithmetic sequence is a sequence in which each term after the first….”
OG Explanation is fine.
Khan Academy Question 247 begins at 4.45

Question 229 – “Right triangle PQR is to be constructed in the xy-plane so that….”
OG Explanation is okay. See Khan video for a better explanation.
Khan Academy #248 Begins at 0.00

Question 230 – “The value of 2^-14 + 2^-15 + ….”
OG Explanation is fine.

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