Question

The cost of papering the four walls of a room at $75$ paise per square metre is $Rs240$. The height of the room is $5$ meters. Find the length and the breadth of the room, if they are in the ratio $5:3$.

• A. $11m$ and $12m$
• B. $20m$ and $12m$
• C. $22m$ and $12m$
• D. $19m$ and $12m$

Answer 1

The correct option is B $20m$ and $12m$

Given, cost of papering the wall is Rs 240 at 75 p per sq. m. Height of the room is 5m and length and breadth are in ratio 5:3.
$Areaofwalltobepapered=\frac{costofpaperingthewall}{costofpaperingpermeter}=\frac{240}{0.75}=320m^2$
Height of wall= $5$ cm.Let length of wall be 5$x$ and breadth be 3$x$.

Surface area of four walls$=2h(l+b)$
$320=2\times 5(5x+3x)320=10\left(8x\right)320=80xx=4$
Length of wall$=5x=5\times 4=20m$.
Breadth of wall$=3x=3\times 4=12m$