Buns cost 40p each
cakes cost 55p each
i spend exactly £4.35 on buns and cakes.
how many of each did i buy?

Lets make an estimation

Lets estimate that 4 buns are bought = 4*40
                                                            = 160 p
                                                            = 1.60 euro

Lets estimate that 5 cakes are bought = 5*55
                                                            = 275 p
                                                            = 2.75 euro

Total money spent = 1.60 + 2.75= 4.35

Therefore,  4 buns and 5 cakes are bought. 

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.