gmat Prep Math Question

[RonPurewal]

It seems that the key to statement to is recognizing that the square root of 1.15 is 1.07. Any suggestions on what is the easiest way to know that other than calculating. Because I can estimate that the square root of 1.15 is between 1 and 2 but down to .07. Not sure how to do that.

you don't need this, actually.

remember, the only issue is how "r" compares with 8. therefore, you can just plug in r = 8 and see how that compares with 1.15.
see this post:
post44164.html#p44164

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in terms of your question -- it really shouldn't take you that long to test 1.07^2 (and a few other such numbers, if necessary). if that takes you a long time, then you should practice that sort of multiplication so that it's not an issue.

[arpitgoel7]

Am I the only one who solved (1+r/100)^2 for (1+r)^2/10000
- There has to be a better way we can write this
Perhaps, (1+(r/100))^2?

[RonPurewal]

Am I the only one who solved (1+r/100)^2 for (1+r)^2/10000
- There has to be a better way we can write this
Perhaps, (1+(r/100))^2?

standard math notation (order of operations) -- division comes before addition, regardless of left-right order. so, this is the default interpretation; no extra grouping symbols are needed.

when it comes to adding extra parentheses, the problem is that you can get into a huge bulk of parentheses very quickly -- and then the problem becomes just as unreadable as it was before.

although i, personally, would put extra space around the plus sign to emphasize the default order:
(1 + r/100)^2
you've probably never noticed this before (why would you?) but ALL math textbooks will do the same thing -- i.e., put extra space around addition and subtraction signs -- just so the default order of operations is more intuitively obvious.