Charge rates used to be simple math and time was easy to predict.

If we really could charge that 5000 mah pack at 10 amps then (and it took 5000 to charge it up) then it is 30 minutes since 10 amps is equal to 10,000 / hr.

The 5000 mah pack at 2.89 amps is 104 minutes since 2.89 amps is equal to 2890 / hr.

In the first example unless the charge rate is held at 10 amps for the full time then it will taper off at 4.2 volts to maintain constant voltage (almost all charge routines use this) and it will slow down the charge. Practically a poor high IR pack with a cheap charger and long skinny leads will take much longer than a high quality new High "C" rated quality smart charger with short fat leads.

In the second example the rate will also not stay constant , but the power will so the 2.89 might be 3.5 at start , but go down to 2.8 or so toward the end. The above problems also exist in this example.

Don't forget that in both cases some chargers stop for brief periods of time and are not accurate for current (both of which slow down the charge) and packs many times are not "empty" (which speeds up the charge)