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9h
comment Given common terms (and their position) between an arithmetic and geometric sequences, find the common ratio.
One might suggest that $r=1,d=0$ giving a constant sequence is contrary to the spirit of the problem and we should only accept $r=3, d=\frac {2x}3$. Well done.
10h
revised How I can prove that for any natural number $n$ such that $30<n$, $\pi(4n-3)<n$?
correct typo
11h
comment Are there sets of zero measure and full Hausdorff dimension?
Then to answer the first question, can't you add/subtract any countable set of points without disturbing the measure (and, I think the dimension) so you get continuum many sets?
12h
comment How many ways are there to choose one-half dozen donuts from $9$ varieties so that there are exactly $4$ glazed?
The first step is to understand the problem. Is glazed one of the $9$ varieties or are some of the varieties glazed? Do you care what order you pick them or just how many of each type you wind up with?
12h
revised Connecting up boxes mathematically (Puzzle)
edited tags
12h
answered Connecting up boxes mathematically (Puzzle)
12h
reviewed Approve Connecting up boxes mathematically (Puzzle)
16h
comment How to prove this curiosity that has to do with cubes of certain numbers?
It lets you manipulate the terms. Now you can expand the cubes and get terms like $10^{3n}, 10^{2n}$ and so on. You will be able to combine the like terms that come from the various pieces.
16h
comment How to prove this curiosity that has to do with cubes of certain numbers?
Alpha says it is $(100^n+2)(10^n-1)/6$
16h
comment How to prove this curiosity that has to do with cubes of certain numbers?
I would write it as $(\frac{10^n-4}6)^3+(5\cdot 10^{n-1})^3+27(\frac {10^n-1}9)^3$ and sort out the terms.
16h
comment How to square a number that got more digits than search results “digits” on Google.
The Babylon method you link to is for calculating square roots, while your question deals with squaring.
19h
answered Expected Number of Draws without Replacement
20h
answered subsets in the cartesian product
20h
reviewed Reject How to get to the formula for the sum of squares of first n numbers?
20h
comment Should an interpolation coincide the original function on the given data points?
If you look at the Wikipedia page it shows various interpolation techniques, all of which produce functions that go exactly through the points.
22h
answered Should an interpolation coincide the original function on the given data points?
1d
awarded  Nice Answer
1d
comment Is it accurate to say that multiplication of two integers yields an integer?
Yes, I was following your example. Generally floats are only accurate to within a factor $1+ \epsilon$, where $\epsilon$ is the smallest number that can be added to $1$ to give a different result. The IEEE standard is discussed here. A 64 bit float has $53$ binary bits in the mantissa, so $\epsilon$ is about $2^{-53}$. This error makes comparisons of equality problematic for floats. You need to think hard about what equality means for you.
1d
comment Is it solvable to ask to find a recurrence relation for the following sequence 4,7,2,20,31,73,155,332,715,… ?
Similar to my statement that giving the extra three values can let you tell them it is a sixth order recurrence, you can use the three values to limit the inhomogeneous part. If you say the inhomogeneous part has degree $2$ or less, they can find it is $0$. You could alternatively allow some variation in the coefficients that the extra three values can rule out, but I haven't thought about how much.
1d
answered Is it solvable to ask to find a recurrence relation for the following sequence 4,7,2,20,31,73,155,332,715,… ?