(UK St Paul's Girls School Sample Paper Section $B$ Question $$2$$)  My money box contains an equal number of $5$p, $10$p and $20$p coins and no other coins. How many coins are there altogether if there is $￡4.90$ in the money box? 
Overseas Competition->Knowledge Point->Counting Modules->Questions Involving Enumeration->Enumeration->Ways of Paying->Calculating the Price