Question

While at camp Mrs Ktenas asked 24 of her year 12 students to plant apple and

orange trees. While each girl planted 3 orange trees, every three boys planted
1 apple tree. By the end of the day, they planted 24 trees. How many apple and
orange trees were planted?
(Also, more than the answer, how would I be able to work this out myself?)​

Answer 1

6 apple trees, 18 orange trees

Explanation:

Let the number of boys be x and the number of girls be y

x+y=24

As each three boys plant 1 tree, each boy plants 1/3 trees

Each girl plants 3 trees

Note that the type of tree is irrelevent at this point as we are working out the number of boys and girls by the total number of trees

x/3+3y=24

x+y=24

Times x/3+3y=24 by 3

x+9y=72

x+y=24

Minus the first equation with the second equation, we get that

8y=48

y=6

substitute into the equation

x+6=24

x=18

As each 3 boys plant a apple tree, total apple trees planted by boys=18/3=6

As each girl plants 3 orange trees, total orange trees planted by girls=6*3=18