22. (4) It may be biased because the majority of drivers surveyed were in the younger age intervals.
I don’t know how to explain this. Choice (1) is no good since under-16s don’t drive. Choice (3) is no good because who cares who did the survey, if it was done right. Choice (2) says lots of ages were surveyed, but Choice (4) is better, since the sample seems to be overwhelmingly skewed to under 35 and even under 25s.

23. (2) $a = \frac{2v}{t^2}$
You can do this in two steps. Multiply both sides by 2:  $2v = at^2$, then divide both sides by $a^2$.

24. (1) $\frac{x+12}{2x+4}$
Since these expressions have a common denominator, just add the numerators.

25. (4) 6,000
There are lots of ways to get this answer. I prefer to change one and a half to 1.5 minutes. $\frac{150 meters}{1.5 minutes} = \frac{M meters}{60 minutes}$. You’ll get M = 60 x 150 / 1.5.

26. (4) 336
There are 8 choices for the first letter times 7 for the second times 6 for the third. These arrangements are also called permutations and can be expressed as $_8P_3$, which your calculator can compute for you. 8 times 7 times 6 is simpler, and makes more immediate sense.

27. (2) 3(x – 3)(x + 2)
Want to know a great trick?  Write the original expression in the calculator as a function:  $Y_1 = 3x^2 - 3x - 18$, and then try out each of the answers in $Y_2$. If they match exactly, they are equivalent, and then you can choose the furthest factored one.
Another trick – multiply each of the answers back together. Three will match the original, and pick the most-factored one.
And not a trick, factor it. Start by pulling out the 3 (now only choices (1) and (2) are possible). See if you can go another step (you can)

June 19, 2010 pm30 7:38 pm 7:38 pm

Are you sure #22 is right? I thought it was choice 2. That was a hard question ’cause both choices 2 and 4 were right!

June 20, 2010 pm30 10:29 pm 10:29 pm

I put the same exact thing, choice 2.

June 20, 2010 am30 4:33 am 4:33 am

number 27 is wrong its 3 not 2

June 20, 2010 am30 10:40 am 10:40 am

Choice 3 isn’t simplified far enough. You need to factor out the GCF before finding the roots, or after you get (3x-9)(x+2) see that you can factor out a 3 which gives you 3(x-3)(x+2).

June 20, 2010 am30 8:57 am 8:57 am

Number #22 was a wierd question

• June 20, 2010 am30 10:47 am 10:47 am

I think that sampling bias belongs in the social studies classroom. Isn’t the opinion polling we care about often related to elections?

4. June 21, 2010 pm30 7:03 pm 7:03 pm

Isn’t 25 choice 3 because it asks for meters per hour so it would be 150/1.5=100?

5. June 21, 2010 pm30 7:11 pm 7:11 pm

25: distance=rate over time…i don’t understand what you did there…

6. June 21, 2010 pm30 7:13 pm 7:13 pm

aw man i see what i did wrong…never mind.