Children are offered a $25 \%$ discount on the cost of an adult ticket to visit Hamshaw House. Senior citizens are given a $20 \%$ discount. If a child's ticket costs £$30$, how much does a senior citizen pay? 
Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Finding the Base Overseas Competition->Knowledge Point->Word Problem Modules->Solving Problems Involving Fractions and Percentages->Knowing the Base