Question

a class room is 7 m long, 6 m broad and 3.5 m high doors and windows occupy an area of 17 square m what is the cost of white washing wallls at the rate of 1.5 per square m​

Answer 1

the cost is Rs. 174

hope u understand it

:)

Answer 2

${\huge{\underline{\underline{\bf{\star Question }}}}}$

Q - A class room is 7 m long , 6 m broad and 3.5 m high doors and windows occupy an area of 17 square m . What is the cost of white washing the walls at the rate of 1.5 square m ?

${\huge{\underline{\underline{\bf{ Answer \checkmark}}}}}$

${\large{\underline{\rm{☆ Given}}}}$

• Length = 7 m
• Breadth = 6 m
• Height = 3.5 m
• Area of doors & windows = 17 m²
• Rate of whitewashing = 1.5/m²

${\large{\underline{\rm{☆ To\;Find}}}}$

• Total Cost of whitewashing = ?

${\huge{\underline{\rm{☆ Solution}}}}$

First , finding the total area to whitewash -

We know , that only 4 walls are to be whitewashed , except door and windows ..

so ,

$\boxed{ \rm \: area _{whitewash} = area _{4 \: walls} - area _{doors \: and \: windows}}$

$\mapsto \rm \: ar _{whitewash} = 2(l + b) \times h - 17 {m}^{2}$

$\mapsto \rm \: ar _{whitewash} = 2 \times 3.5(7 + 6) - 17 \: {m}^{2}$

$\mapsto \rm \: ar _{whitewash} = 7 \times 13 - 17 \: {m}^{2}$

$\rm \mapsto \: ar _{whitewash} = 91 - 17 \: {m}^{2}$

$\mapsto \boxed{ \rm \: area _{whitewash} = 74 \: {m}^{2} }$

Now ,

Finding the Total Cost now ..

$\boxed{ \rm \: cost = rate \times area}$

$\mapsto \rm \: cost = \frac{1.5}{ \cancel{{m}^{2} }} \times 74 \: \cancel{{m}^{2} }$

$\mapsto \rm \: cost \: = 1.5 \times 74 \: rupees$

$\mapsto \boxed{ \rm \:cost = 111 \: rupees}$

So ,

The cost of whitewashing would be 111 Rs .

________

${\large{\underline{\rm{☆ Know\;More:-}}}}$

• $\sf \: area \: of \: 4 \: walls = 2(l + b) \times h$
• $\sf \: cost \: = rate \times area$
• $\sf \: tsa = 2(lb + bh + lh)$
• Area is always in unit square (u²)