240 students of a school are arranged in rows. If 4 students would be less in a row then 3 more rows

M4maths Previous Puzzles

01 Mar 2011 school

240 students of a school are arranged in rows. If 4 students would be less in a row then 3 more rows will be arranged. Initially total no of rows will be.

OPtion

1) 6
2) 8
3) 10
4) 12
5) 15
6) 16
7) 18
8) 20
9) 24
10) 30

Solution

Let no. of rows = x and no. of students in a row = y
According to the given conditions
x.y = 240 (1)
(x+3).(y-4) = 240 (2)
or (x+3).[(240/x)-4] = 240
or (x+3).[240-4x] = 240x
or 240x - 4x^2 + 720 - 12x = 240x
or x^2 + 3x - 180 = 0
or x = 12, -15

Correct Option: 4 Best Solution (12)

sanjeev   13 years AGO

we start by checking the options...start
ans is initially there were 12 rows..
.
now check..
240/12=20..means in one row 20 students were sitting..initially
now we reduce 4 students from each row we have 16 students in each row..means 12*16=192 students...
now as according to question 3 more rows will be increased by reducing 4 students...so remaning will be sited in the increased rows i.e (16*3=48
where 16 is no of students n 3 is no of increased rows) so 0verall 192+48=240...
.
so..initially there were 12 rows...

Like? Yes (5) | No   

krishna kumar gupta   13 years AGO

let number of rows=x;
then no of student in each row=240/x;
according to question----
x+3=240/((240/x)-4)
x=12
so initialy no of rows=12

Like? Yes (2) | No   

dharmaveer   13 years AGO

if 20 students arranged in each row then the number of rows will be 240/20=12

and if we 4 students less in each row mean 20-4=16 members in each row then the number of rows will be 240/16=15

Like? Yes (2) | No   

YadeeshKumar   13 years AGO

20 members sit in 12 rows each.(20*12=240)
now,4 members less in each row.
thats 16 members in a row.
so 16 members can sit in 15 rows (16*15=240)
(that increases 3 more rows from question)

Like? Yes (2) | No   

goutam Choudhury   13 years AGO

Initialy rows were 12 and no. of students were 20. 20*12=240.then students were 20-4=16 and rows were 12+3=15. 16*15=240.

Like? Yes (1) | No   

sandeep reddy m   13 years AGO

xy=240
x-4 * y+3 =240
x=20 students
y=12 rows

Like? Yes (1) | No   

kartik   13 years AGO

let consider no. of students in each row is x and no. of rows is y.
then x*y=24
and (x-4)*(y+3)=240
solve the above equations and get the value of y. that will be the answer

Like? Yes (1) | No   

Dr.Dipin Singh   13 years AGO

240= 20 students in 12 rows
240= 16 students in 15 rows.

Like? Yes (1) | No   

Dimple   13 years AGO

Initially x students in each row and y rowa are there.

Then
x*y=240
(x-4)*(y+3) =240

solving it, we get
y=12 rows.

Like? Yes (1) | No   

shubham srivastava   13 years AGO

(x rows)*(y students/row)=240
(x+3)*(y-4)=240

Like? Yes (1) | No   

giri prasad   13 years AGO

initially the number of students were 240 i.e assume each row has 20 members
if u remove 4 members then each row will be 16 members.
then the rows are 15
20*12==16*15==240
there initially the number of rows are 12

Like? Yes (1) | No (1)  

~Sandeep~   13 years AGO

12 * 20 = (12+3) * (20-4).
So 12 is the no. of rows (Option 4)

Like? Yes (1) | No (1)