Maths in SAT Watch

e-n-i-g-m-a
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Q.1 If f(x) = x^2 + cubicroot x , what is the value of f(-8)?

In this case we can we take the cube root of x = -8 .. i mean isn't it a rule that we can get the square root of a negative number !

Q.2 Because her test turned out to be more difficult than she intended it to be, a teacher decided to adjust the grades by deducting only half the number of points a student missed. e.g, if a student missed 10 points, she received 95 instead of a 90. Before the grades were adjusted, the class average on the test was A. What was the average after the adjustment.

we have to give the answer in terms of A but the question totally confuses me !!
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Chewwy
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1) as said yourself, you're not taking the square root... what is (-2)^3?

2) call the individual marks a_1,a_2,...,a_n

A = (a_1+a_2+...+a_n)/n

new average = ((100 - (100-a_1)/2) + (100 - (100-a_2)/2) + ... (100 - (100-a_n)/2))/n = (a_1+100 + a_2+100 +... a_n+100)/2n = A/2 + 50

using the old sigma makes things look a little neater...
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ImperceptibleNinja
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Q1:
N.B. 'Cube' root, not 'square' root. See if that helps you get going with that one.
[Edit: gah, I was too slow...:rolleyes:]
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e-n-i-g-m-a
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thanks for the help ! can u just help me with one more !

Q.1 Ellie is dropping marbles into a box one at a time in the following order: red,white, white, blue, blue ,blue; red, white, white, blue, blue; .... How many marbles will be in the box right after the 100th blue one is put in ?
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Chewwy
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for every 2 blues put in, a total of 5 are put in. hence 5*50=250
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frixis
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ok i didnt get the logic for the last one...
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bob_54321
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actually, you've written two different orders, the first one has 3 blues, the second has two. if it is 2 then yes, the answer is 250. if it is 3, however, there are 6 for every 3 so after 99 there are 198. then you need another blue so have to put 4 more in (red, white, white, blue) to make 202.
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