I explained to a ten year old girl like this.
First weighing: Take any six coins from these eight and weigh three on each side of the scale.
Option 1:
If they are equal, all the six coins are good ones.
Second weighing: Take any two coins from the remaining three and balance one on each side of the scale.
If they are equal, the left out coin is the fake one; if not equal, the lighter coin is the fake one.
Option 2:
If in the first weighing, one set is lighter, the lighter set of three coins has the fake one.
The second weighing is the same as above, with these three coins, to spot the fake one. :)
First weighing: Take any six coins from these eight and weigh three on each side of the scale.
Option 1:
If they are equal, all the six coins are good ones.
Second weighing: Take any two coins from the remaining three and balance one on each side of the scale.
If they are equal, the left out coin is the fake one; if not equal, the lighter coin is the fake one.
Option 2:
If in the first weighing, one set is lighter, the lighter set of three coins has the fake one.
The second weighing is the same as above, with these three coins, to spot the fake one. :)