Wikipedia:Reference desk/Archives/Computing/2014 October 12

= October 12 =

Help with Excel
Hi! Please let me know if this is not the right kind of question to ask here, but is there a way to reengineer the following formula in Excel so that I get the value of x? All variables other than x are known. PMT is one of the functions in Excel.

c = PMT(r,t,x,ax) + bx

Thanks! ReluctantPhilosopher (talk) 04:55, 12 October 2014 (UTC)


 * Two approaches come to mind. One would be to turn on the iterative calculation option (under Tools > Options > Calculations in my very old version of Excel).  The other would be to solve the problem algebraically.
 * In the first approach, observe that x = present value (PV) and payment (PMT) = c-bx, so you can change the calculation to something like x = PV(r,t,c-bx,ax). If you define cells for a, b, c, r, and t, plus a cell for x defined using the above calculation, Excel will initially complain about a circular reference.  But when you enable iterative calculations, you should get a solution.
 * With the second approach, you need to start with the underlying calculations for future value calculations. By combining the "Future Value - Lump Sum" and "Future Value - Annuity" calculations found on this page, I get:

FV = PV*(1+i)^n + PMT*(((1+i)^n-i)/i), or FV = PV*(1+RATE)^NPER + PMT*(((1+RATE)^NPER-RATE)/RATE)
 * Substituting FV = a*x, PV = x, RATE = i = r, NPER = n = t, and PMT = c-bx, and then manipulating the equation to isolate x, I get:

a*x = x*(1+r)^t + (c-bx)*(((1+r)^t-r)/r) a*x = x*(1+r)^t + c*(((1+r)^t-r)/r) - bx*(((1+r)^t-r)/r) a*x - x*(1+r)^t + bx*(((1+r)^t-r)/r) = c*(((1+r)^t-r)/r) x * (a - (1+r)^t + b*(((1+r)^t-r)/r)) = c*(((1+r)^t-r)/r) x = c*(((1+r)^t-r)/r) / (a - (1+r)^t + b*(((1+r)^t-r)/r))
 * Some further simplification is possible, but (if I haven't made any mistakes) the above should yield your desired result. --  Tom N  talk/contrib 09:56, 12 October 2014 (UTC)
 * Hi Tom. Thanks for the effort! Your calculations look alright but unfortunately i'm not able arrive the at the desired result using it. Dunno what to do next! ReluctantPhilosopher (talk) 05:55, 15 October 2014 (UTC)

Looking for a motherboard
Hi there,

I am planning to custom build a PC. I have everything except a motherboard.

I am searching for a X64 bit overclockable motherboard that has the following minimum specifications: LGA 775 socket, 4 X SATA ports, 2 X IDE ports, VGA ports, good integrated graphics [enough to run Windows 7 Ultimate SP1 X64 bit (minimum 1000 MB total)], 4 X DDR3 RAM 1333 MHz or 2 X DDR3 RAM 1333 MHz and 2 X DDR2 RAM 1066 MHz (If in case 4 X DDR3 RAM 1333 MHz is not available, I will be able to use both 2 X DDR3 RAM 1333 MHz and 2 X DDR2 RAM 1066 MHz) Dual Channel Memory Architecture minimum 8 GB, 8 X USB ports (4 X USB ports on I/O Panel and 4 X USB ports at mid-board), good audio (Realtek HD Audio) and video quality, 2 X fan (1 X processor and 1 X case/chassis), microATX form factor.

I have searched and came to two motherboards: ASUS P541T-M LX3 and Gigabyte GA-G41M Which of the two is better? Is there a better motherboard? I would be very glad if the sites for purchase would be given (preferably Indian), if there is a better motherboard.

I use a computer for programming, making high-end presentations, rendering images and videos and watching movies.

I currently have the following parts: Processor: Intel Pentium Dual Core E2160 @1.80 GHz Hard Disk 1: Western Digital Caviar Blue 500 GB 7200 rpm 3 Gb/s WD5000AAKS Hard Disk 2: Hitachi Deskstar 160 GB 7200 rpm 3 Gb/s HDS721616PLA380 RAM 1: 3 X 1 GB DDR2 667 MHz RAM 2: 3 X 2 GB DDR3 1333 MHz RAM 3: 1 X 4 GB DDR3 (Think it's 667 MHz) DVD 1: Transcend TS8XDVDRW-K (External) (USB) DVD 2: LG HL-DT-ST-DVD-RAM GSA-H55N (not sure) (think it's 48 X) (IDE) (Internal) Stock/Processor fan: Cooler Master Combo with Heat Sink [(2500-3500 rpm 12VDC) (I have seen on 250W PSU/SMPS)] Case/Chassis fan 1: SUNON [(2500-3500 rpm 12VDC) (I have seen on 250W PSU/SMPS)] Case/Chassis fan 2: Thermal Cooler [(2500-3500 rpm 12VDC) (I have seen on 250W PSU/SMPS)] (Temperature: 27-42 Celsius) Case: HCL Home Server Case (from old comp) PSU/SMPS: Delta Electronics 250W 24 pin ATX (6 years 3 months old) Mouse 1: Logitech M185 (Wireless) (Infra-red) (USB) Mouse 2: Logitech (USB) Mouse 3: Logitech (USB) Keyboard 1: Logitech K120 (USB) Keyboard 2: Logitech (PS2) Display: HCL HCM782M 17" CRT Monitor

I would be very glad if any tips or advice is given. I am also searching for a good 450W PSU/SMPS. Is it good to wrap HDD in foam to prevent noise?

Thanks

Aravindv.nair1999 10:00, 12 October 2014 (UTC) — Preceding unsigned comment added by Aravindv.nair1999 (talk • contribs)


 * , either brand would be good. I prefer Asus, but it is personal opinion. Whatever's cheaper, really. As for PSU, Corsair, Seasonic, and EVGA are good brands. Some PSUs are just repackaged PSUs from other brands, so do your research before buying.  Konveyor   Belt   18:38, 13 October 2014 (UTC)

Excel numbering
Hi-

I'm working on an Excel spreadsheet that seems to have renumbered itself (I'm sure this is my fault; I'm just not sure how) - what it looks like is what you see here. What I want to do is reset the row numbering to default -- so 198 should be 2, 199 should be 3, etc. I'm using the most recent version of Excel Online and, as far as I can tell, it was engineered by Satan to drive me insane. I'm sure there's a simple solution, but I've been through so many tutorials today my brain is fried. Any help? 71.28.114.225 (talk) 18:55, 12 October 2014 (UTC)


 * Start off by disabling the filter on column G. That will hopefully unhide the rows that you're currently not seeing. --David Biddulph (talk) 19:58, 12 October 2014 (UTC)
 * Yup, I should have thought of that. Someone mangled this file before I got round to it. Fixed now, thanks! 71.28.114.225 (talk) 20:15, 12 October 2014 (UTC)