<p>Q. If ab+b = a+2c, what is the value of b when a=2 and c=3? </p>
<p>Help.</p>
<p>Edit: nevermind, i got it.</p>
<p>Another question:
If the sum of consecutive integers from -22 to x, inclusive, is 72, what is the value of x?</p>
<p>A.23
b.25
c.50
d.75
E.94</p>
<p>Is there a formula for this type of q?</p>
<p>What are the answer choices? Questions this hard are generally easier if we had choices to choose from.</p>
<p>Are you serious, Quix? b= 8/3</p>
<p>I pray to God he was joking. Every time someone posts such a stupid thread, God kills a panda.</p>
<p>I misread the first question lol. Help me out with the other question guys. </p>
<p>and kho, sometimes questions dont have choices for you to choose from because they're grid ins. </p>
<p>Pandas are already extinct, have you seen the number of posts on that other thread?</p>
<p>Quix, -22 to x is 72 is a rather easy problem....</p>
<p>map it out:</p>
<p>-22-21-20-19-18-17-16......0.1+2+3+4+5+6....so -22 to 22 negates each other</p>
<p>-22+22 = 0
-21+21 = 0
-20+20 = 0</p>
<p>and so on..</p>
<p>so start from 23+24+25....=72 there you have it.</p>
<p>Total calculation time ... 15 seconds</p>
<p>EDIT: The same type of reasoning/logic goes for a problem that asks for the # of #s added from so-and-so (negative) to so-and-so. Just don't forget to add the inclusive 0..</p>
<p>Omg. I did the same thing and then added 1+2+3 instead of 23+24=25 for some reason.
Im not thinking clearly today, i haven't slept in 17 hours. </p>
<p>Im going to take a nap. Thanks guys.</p>
<p>And to speed that up, find the average of 72+23 and multiply it by 50.</p>
<p>amciw, what are you talking about?</p>
<p>And Quix, my first post was obviously sarcastic...</p>
<p>The question is a pre algebra problem, not even an algebra one. Its just sticking in numbers. My brother can do it and hes in like 5th grade.</p>
<p>^ I believe amciw was referring to the 2nd problem Quix posed...although I'm not sure what he means.</p>
<p>amciw i think you're more confused than i am.</p>
<p>Kho, you'd be surprised about how many posters ask that question. Its not obvious, how do i know you're not one of "those" guys? And i don't need you to tell me that the question's easy-as i mentioned earlier, i misread the question. I don't care what your brother can do, i'm sure he's just as special as you. There are such thing as human beings who would kill themselves trying to solve that "pre algebra question", CC is not limited to elite SAT test takers and there's bound to be some kid who needs to brush up on his basics. If you're going to stick your head in these threads just to criticize, then you're obviously no better then the kid who's about to mark up his entire test for a 2400.</p>
<p>Good night.</p>
<p>The second problem you posted. If you haven't taken calculus, the concept might be a bit harder to grasp.</p>
<p>You can just see the whole problem as a basic integration problem, with a line of y=x as the derivative. The integer value is the rate at which the summation changes. To find the whole summation, you just find the area under the graph from 23 to 72. There is a theorem in calculus, that I forgot the name of, that says you can just take the average value of the range of y-values and multiply it by the range in x-values, to find the answer.</p>
<p>Of course, as I also just realized, you could simply integrate the line y=x to get y=(1/2)x^2 and solve the problem by doing f(72)-f(23), or you could just put y=x in your graphing calculator and use the integrate feature to do all the hard work for you.</p>
<p>You have some of the numbers wrong. 23 and 72 are not the numbers that we need to use.</p>
<p>And your calculus is a little off as well. Integrating the equation y = x from 23 to 72 is not the same as adding the numbers from 23 to 72.You would need a step function to do the integration correctly. Integrating from 23 to 72 is like adding 23.5, 24.5, 25.5, ... , 71.5.</p>
<p>Using your integration technique, the sum of the integers from a to b would be. (b^2 - a^2)/2.
The true equation is (b^2 - a^2 + b + a)/2.</p>
<p>You can see where your equation clearly fails when either the starting or the ending number is odd and the other is even. The resulting answer will have .5 as a decimal. Adding integers together will never yield a decimal as part of the answer.</p>
<p>You didn't need to elaborate. I see my mistake, and that I wasn't thinking very clearly.</p>
<p>However, the first part is still right, my second paragraph. Adding up 23 to 72 on the calculator and using the method derived from the calculus theorem yielded the same answer.</p>
<p>No, my point was that even the second part was incorrect. You cannot integrate the equation y = x to add together a series of integers.</p>
<p>I know the second part is incorrect. Its the third paragraph in my post, though.</p>
<p>
[quote]
Kho, you'd be surprised about how many posters ask that question. Its not obvious, how do i know you're not one of "those" guys? And i don't need you to tell me that the question's easy-as i mentioned earlier, i misread the question. I don't care what your brother can do, i'm sure he's just as special as you. There are such thing as human beings who would kill themselves trying to solve that "pre algebra question", CC is not limited to elite SAT test takers and there's bound to be some kid who needs to brush up on his basics. If you're going to stick your head in these threads just to criticize, then you're obviously no better then the kid who's about to mark up his entire test for a 2400.
[/quote]
</p>
<p>Amen .</p>
<p>As I just realized, you are taking a Riemann Sum on the range, with midpoints at each integer from 23 to 72. Naturally, the end of each section would be .5 to the left and right of the midpoint, so the first added up section goes from 22.5 to 23.5. Since midpoint Riemanns are the area under the graph when the graph in question is linear, you could integrate f(x)=x and take f(72.5) - f(22.5) to get the correct answer.</p>