Question

12) The length of a room is 15 m and its breadth is double
its height. If the area of four walls of the room is 250 sq.m,
breadth of the room is:
Is a lot
oo
uis
A) 5 m
B) 8 m
C)​

Answer 1

Question - The length of a room is 15 m and its breadth is double its height. If the area of four walls of room is 250 sq.m breadth of a room is :

A 5m

B 8m

C 10m

D 19m

Given - Length of room - 15 metre

Breadth of room - 2*height

Area of four walls - 250 metre².

Find - Breadth of room.

Solution - Area of four walls of room is given be the formula - 2*h(l+b). In the formula, h is height, l is length and b is breadth.

250 = 2*h(15 + 2*h)

250 = 30*h + 4*h²

4h² + 30h - 250 = 0

Solving the equation -

(-30 ± ✓900 + 4000)/2*4

(-30 ± ✓4900)/8

(-30 ± 70)/8

(-30-70)/8 and (-30+70)/8

-100/8 and 40/8

Since height can not be negative, 40/8 or 5 will be the value of height.

Now, as per question, breadth is twice the height. So, breadth = 2*5 = 10 metres.

Hence the correct answer is C 10m.

Answer 2

Given : The length of a room is 15 m and its breadth is double its height. the area of four walls of the room is 250 sq.m,

To Find : breadth of the room  

A) 5 m

B) 8 m

10 m

Solution:

breadth of the room   = B  m

Height of room = B/2  m

length of a room is 15 m

Area of 4 walls = 2(l + b) h

= 2(15 + B) B/2  = 250

=> B² + 15B  = 250

=> B²  + 25B - 10B - 250 = 0

=> (B + 25)(B - 10) = 0

=> B = 10  as B can not be negative

Breadth = 10m

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