Angela has £15.76. she buys as many bottles of drink costing £1.20 each as she can. how many does she buy and how much money does she have left?

without calc pls and show working out pls

One way of doing it is to realize that if she buys 5 bottles, she would need exactly $6. $15.76 that she has includes 2 $6's, which means that she can buy at least 10 bottles. After these 10 bottles, she would have spent $12, therefore having $3.76 left. This is enough for 3 more bottles, costing $3.6 total. 3.76-3.6=$0.16, which is the amount she has left over, after buying a total of 13 bottles.