Question

The surface area of a cuboid is $1300c{m}^2.$ If its breadth is 10 cm and height is 20 cm, find its length.

Answer 1

$\text{Surface area of a cuboid}=1300c{m}^2$

$\text{Breadth (b)}=10cm$

$\text{and height (h)}=20cm$

$\text{Let l be the length, then}$

$2(lb+bh+hl)=1300$

$lb+bh+hl=\frac{1300}{2}=650$

$l\times 10+10\times 20+20\times l=650$

$10l+20l+200=650$

$\Rightarrow 30l=650-200=450$

$\Rightarrow l=\frac{450}{30}=15$

$\therefore \text{Length of cuboid}=15cm$