After Tasneen's birthday, half of the cake was left over. Tasneen and his four friends are only allowed to eat \( \frac{1}{5} \) of the half cake. What fraction of the whole cake will Tasneen and his friends have eaten after his birthday party?

Tasneen's birthday cake has half left over after the party. If they can eat \( \frac{1}{5} \) of that half, we can calculate it as follows: First, find \( \frac{1}{5} \) of the half cake: \[ \frac{1}{5} \times \frac{1}{2} = \frac{1}{10} \] Thus, Tasneen and his friends will eat \( \frac{1}{10} \) of the whole cake after the party. So, the fraction of the whole cake they consumed is \( \frac{1}{10} \).