There are 45 pupils in a class, 1/9 travel to school by train, 2/5 travel to school by car, 2/9 take the bus. Find how many students walk

First the number of children that travel by train can be found by dividing 45 by 9 to give 5. Since we know that double as many take the bus, as 2/9 is the double of 1/9,5x2=10 children take the bus. Then we can find how many travel by car by dividing 45 by 5 and then multiplying by 2, 45/5=9, 9x2=18. Finally these numbers can be added to give 18+5+10=33 and then subtracted from 45 to find how many children walk. Therefore 45-33=12 children walk to school.