how many mole left if I rinse it for many times?

[Grason]

A vessel contains a solution of concentration X mole/L. On emptying the vessel, 0.1 ml of the solution remains adhered to the glass. How many moles of material the left inside the vessel?

If 10ml of deionized water are added, rinsed round and tipped out, so that again 0.1 ml of liquid is left behind, how many moles of material are now left?

If this rinsing procedure is repeated with a further 10 ml of deionizd water, how many moles of material remain now?

If the vessel is rinsed only once with 20 ml of deionized water, inside of rinsing with two 10 ml portions of deionized water, and again 0.1 ml of liquid is left behind, how many moles of material remain in this case?

In this example, how many times more effective is it to wash twice with 10 ml of deionized water than to wash once with the same total quantity(20 ml)?