Question

please tell fast with explanation.....

Answer 1

We are given, (l+b+h) = 19

Hence, (l+b+h)^2 = 361

=> l^2 + b^2 + h^2 + 2lb + 2bh + 2lh = 361 ..................(1)

Length of diagonal = 11 cm

= √(l^2+b^2+h^2) = 11

squaring both sides

l^2 + b^2 + h^2 = 121 .................................(2)

putting value from (2) in (1)

121 + 2(lb+bh+lh) = 361

hence, 2(lb+bh+lh) = 361 -121 = 240

Hence, Surface area is 240 cm^2.