Our collection of bottle tops seem to grow at the same rate as used toilet rolls! Fast! To reduce,reuse,recycle...we decided to make a mathematical problem solving game. I marked out the bottle tops with numbers 1-12 as well as the + - and = signs. I made up an equation and Tara had to choose her bottle top answer. Then she made one for me and so forth. Its a great little activity that can grow with your child. leaving out a part of the middle of the equation or adding times by or percentages.