Tom is making gift bags, each of which will contain two balloons. He wants to hide a sweet in one of the balloons. 20 balloons cost £1.33, 15 sweets cost £2.05. What is the minimum he needs to spend to make 35 bags?

First work out how many balloons he will need to buy. In order for each bag to have two balloons, he will need 70 balloons. Since he can buy 20 balloons at a time, this implies the minimum number he would need is 80 balloons (as it is the smallest multiple of 20 which is bigger than 70 – use number line to help visualise), or four bags of balloons. Therefore he needs to spend 4 times £1.33 on balloons, i.e. he needs to spend £5.32 on balloons.Now let’s work out the same thing but for sweets. Since only one of the balloons will have a sweet inside it, each bag only needs one sweet meaning he only needs to get 35 sweets. Since he can only buy 15 sweets at a time, this implies the minimum number he would need is 45 sweets (as it is the smallest multiple of 15 which is bigger than 35), or three bags of sweets. Therefore he needs to spend 3 times £2.05 on sweets, i.e. he needs to spend £6.15 on sweets.Finally, we need to add these two numbers together to get the total cost of the gift bags, meaning they will cost a total of £5.32+£6.15=£11.47