I am looking into buying a fast card reader, and concluded that to transfer $8 GB$ of data $(8\cdot 1024 MB)$ to my computer at a data transfer speed of $130 MB/s$ would take me $1.024$ minutes. gigabytes / data transfer speed per second / time in second = transfer time in minutes
(8*1024 megabytes) / 130 megabytes / 60 = 1.024.
Then I wondered what my current card reader's transfer speed was, although system preferences shows it can transfer UP to 5 GB per second. Thats not accurate. I only have this information:
"It took me 14 minutes to transfer the data and I transferred $8 GB$ of data"
How do I change the formula so that data transfer speed is the subject? data transfer speed =
I am trying to take the mathematical approach rather than just working it out in my head, which would be $\frac{8\cdot1024}{14\cdot60}$ which will give me $9.75 MB/s$.
This is all well and said but whats the correct way to adjust the formula step by step?
This is what I have so far:
gb / dataTransferSpeed ps / time in second = transfer time in minutes
gB / dataTransferSpeed ps = transfer time in minutes * time in second
But then I dont seem to know how to change it from there on? any help will be great
It's a nice idea to rearrange your formula. By using your notation you can do it like this
(reapeating your last line with fancy formulas:): $$\small\frac{\text{gB}}{\text{dataTransferSpeed ps}} = \text{transfer time in minutes} \cdot \text{time in seconds}$$ Then $\cdot \text{ dataTransferSpeed ps}$ on both sides yields
$$\small\text{gB} = \text{transfer time in minutes} \cdot \text{time in seconds} \cdot \text{dataTransferSpeed ps}$$
Then you could try $\div (\text{transfer time in minutes} \cdot \text{time in seconds})$ on both sides which will give you the result. (This is not the most elegant or fastest way to do this, but this uses the work you already did.)
While this should solve your problem, I want to show a little more since you don't seem to be completely aware of what exactly you are doing. (By writing gB you implicitly mean the amount of GB in MB, but when it comes to seconds and minutes you do this explicitly etc.)
Well, the data transfer speed is defined as the amount of data you can transfer per time unit. So if we call data transfer speed $R$ (for 'rate'), the amount of data $d$ and the time $t$, then $$R=\frac{d}{t}.$$
So in short, this is the answer to "data transfer speed= ?".
When considering
we have $t=14$ min, $d=8$ GB. Applying our formula above yields
$$R=\frac{8\text{ GB}}{14\text{ min}}=\frac{8}{14}\cdot\frac{\text{GB}}{\text{min}} .$$
Everything you do afterwards is just changing the units (in our example the $\frac{\text{GB}}{\text{min}}$ part). Since
1 GB = 1024 MB and
1 min = 60 s,
we can plug this in: $$R=\frac{8}{14}\cdot\frac{\text{GB}}{\text{min}}=\frac{8}{14}\cdot\frac{1024\text{ MB}}{60\text{ s}}=\frac{8\cdot 1024}{14\cdot 60}\cdot\frac{\text{MB}}{\text{s}}$$
There is no simple formula for this in general (in the sense that you can't put any amount of data and time in while using various units and still expect a result in MB/s) because the result depends on the units. If you want to have a result in MB/s you need to change any occuring units (like GB, TB, B, KB, minutes, hours, days) to MB or seconds respectively - as we did above.
Of course, there is some difference if you already know which units you will have available. If you know the amount of data in GB (call this $d_{\text{GB}}$) and the amount of time in minutes (call this $t_\text{min}$) and you want to get the result in MB/s, you can adjust the formula to $$R=\frac{d_\text{GB}\cdot 1024}{t_\text{min}\cdot 60}.$$