mumworks:

Hi,


Besides using guess and check, any better way to solve this problem ?

360 teachers and pupils participated in tree planting.
Each teacher planted 3 trees and each group of 3 pupils planted 2 trees.
If 520 trees were planted altogether, how many pupils were there ?

Thanks in advance.

Hi,

I am not sure if I am right but we can use equation:

360 = T + S (T-teachers and S-Student)
520 = 3T+2S/3 (Total numbers of trees)
.
....

You will get S= 240 (there are 240 students)

Check answer:
240 (students) + 120 Teachers = 360
(240/3)2+(3*120) = 520 trees

So I am not guessing my answer right?