QR question from DESTROYER

[kov82]

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88) it asks between 10 and 90 you can never assume they mean 11-89? as a trick?


123) (996)^1/3 , I understand using 1000 to approximate but the actual answer is based on the approximation, is this type of thing done on the DAT?

137) how can you know its a triangle? I drew a square



I know using CAST that cos is positive in quadrant 4 All are positive in q 1 sin in q2 and tan q 3, but which quadrants are csc sec cot positive?


If I need to approximate (15)^1/2 and my answer choices are 2.1, 2.7, 3.9, 4.2, 4.4 I can think of 9 and 25 putting my answer between 3 & 5 eliminating the first 2 choices, I could guess 4.4 is not it but how do I choose between 3.9 and 4.2?

 

[ajlst11]

Think of it like this, 15^1/2 = the square root of 15. So, the square root of 16 = 4, right? Now 15 is less than sixteen by a little bit. Since it is less than 16, the square root of 15 HAS to be less than 4, by not much though. The 2.7 is just not correct because 2.7 squared is less than 9, obviously. So the 3.9 is the ONLY possibility for this question. Hope it helps.

 

[Streetwolf]

88) it asks between 10 and 90 you can never assume they mean 11-89? as a trick?

Unfortunately not all problems are crystal clear on this. Usually inclusive means include the 10 and 90 while exclusive would be 11-89. But not all problems say those words.

123) (996)^1/3 , I understand using 1000 to approximate but the actual answer is based on the approximation, is this type of thing done on the DAT?

There's no reason you can't use 1000 to approximate it. 996 is VERY close to 1000. The cube root of 1000 is 10. Do you know what 9^3 is? It is 729. That means 729^(1/3) = 9. That's VERY far from 996. Your answer will be *almost* 10.

137) how can you know its a triangle? I drew a square

Don't know the problem. Don't have the book.

I know using CAST that cos is positive in quadrant 4 All are positive in q 1 sin in q2 and tan q 3, but which quadrants are csc sec cot positive?

I prefer another way to remember it, that keeps the quadrants in order, but use what you want. I use ASTC "All Students Take Calculus". This goes in order from Quadrant I through Quadrant IV. It denotes the positive trig function, so in Quad I all of them are positive, in Quad II the Sine function is positive, and so forth.

CSC, SEC, and COT pair up with their counterparts of SIN, COS, and TAN respectively. Thus where SIN is positive, CSC is positive. Remember that CSC is just 1/SIN, etc.


If I need to approximate (15)^1/2 and my answer choices are 2.1, 2.7, 3.9, 4.2, 4.4 I can think of 9 and 25 putting my answer between 3 & 5 eliminating the first 2 choices, I could guess 4.4 is not it but how do I choose between 3.9 and 4.2?

This was answered above. You forgot that 16^(1/2) = 4.

Answers above in bold.