Question

please solve the question for brilliantlist

Answer 1

Let the number of rows be x and the number of students in a row be y.

So, the total number of students = xy.

(i)

3 students less were standing in each row. 10 more rows were required.

⇒ (y - 3)(x + 10) = xy

⇒ xy + 10y - 3x - 30 = xy

⇒ -3x + 10y = 30

⇒ 3x - 10y = -30   ------ (1)

(ii)

Given, 5 more students were standing then the numbers of rows were reduced by 10.

⇒ (y + 5)(x - 10) = xy

⇒ xy - 10y + 5x - 50 = xy

⇒ 5x - 10y = 50    ------ (2)

On solving (1) & (2), we get

⇒ 3x - 10y = -30

⇒ 5x - 10y = 50

   -------------------

    -2x = -80

       x = 40.

Substitute x = 40 in (1), we get

⇒ 3x - 10y = -30

⇒ 3(40) - 10y = -30

⇒ 120 - 10y = -30

⇒ -10y = -30 - 120

⇒ y = 15.

Therefore, number of students = xy = 600.

Hope this helps!

Answer 2

Hi there!
Here's the answer:

•°•°•°•°•°<><><<><>><><>°•°•°•°•°

Let the no. of student standing in each row be x
& let no. of rows be y

•°• Total No. of students
= (no. of rows × no. of students per row)
= xy

Given,
(x-3)(y+10) = xy
=> x(y+10) -3(y+10) = xy
=> xy + 10x -3y - 30 = xy
=> 10x -3y = 30 __________(1)

And also given,
(x+5)(y-10) = xy
=> x(y-10) +5(y-10) = xy
=> xy - 10x + 5y - 50 = xy
=> -10x +5y = 50 ___________(2)

Add (1) & (2),
=> 10x -3y -10x +5y = 30 + 50
=> 2y = 80

•°• y = 40

From (1),
10x = 3y+30
=> x= (1/10)(3y+30)

substitute y= 40
=> x = (1/10)[3(40)+30]
=> x = (1/10)[120+30]
=> x = (1/10)[150]

•°• x = 15

•°• x×y = 15×40 = 600

•°• No. of students participating the drill = 600

•°•°•°•°•°<><><<><>><><>°•°•°•°•°

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:)

Hope it helps