Question 1034923
2400 students.
60% are boys.
that means that .6 * 2400 = 1440 are boys.
that means that 2400 - 1440 = 960 are girls.
some of the boys went to the field to pitch tents.
this means that none of the girls went to the field to pitch tents.
40% of the students that did not go to pitch tents were boys.
you have 960 girls remaining in the hall and some boys.
the boys made up 40% of the students remaining in the hall.
let x = the number of boys who stayed behind.
they represent 40% of the total students that stayed behind.
the total students that stayed behind are x + 960.
x = 40% of that.
the equation is x = .4 * (x + 960)
simplify this equation to get x = .4x + .4*960.
simplify further to get x = .4x + 384
subtract .4x from both sides of the equation to get .6x = 384
divide both sides of this equation by .6 to get x = 384/.6 = 640.
there were 640 boys who remained in the hall and didn't go to pitch tents.
total who stayed behind were 960 + 640 = 1600.
boys were 40% of that = .4 * 1600 = 640.
since there were a total of 1440 boys and 640 stayed behind, then the number of boys who went to pitch tents is equal to 1440 - 640 = 800.
your solution is that 800 boys went to pitch tents.