Watch the video to see how Charlie works out the sum. Can you adapt his method?
Ben, Jack and Emma passed counters to each other and ended with the same number of counters. How many did they start with?
How many solutions can you find to this sum? Each of the different letters stands for a different number.
Can you do a little mathematical detective work to figure out which number has been wiped out?
Have a go at creating these images based on circles. What do you notice about the areas of the different sections?
How many intersections do you expect from four straight lines ? Which three lines enclose a triangle with negative co-ordinates for every point ?