Question

Find the missing dimension in the figure with given surface area... ​

Answer 1

Answer:

Given

b=5:h=12cm

SURFACE AREA =256cm2

2h(l+b)=256

2.12(l+5)=256

24(l+5)=256

l+5=256/24

l+5=10.666

l=10.666+5

l=15.666

Answer 2

Answer:

$sa = 256 \\ sa \: of \: cuboid = 2(lb + bh + hl) \\ 256 = 2(5l + 12 \times 5 + 12l) \\ 256 = 2(5l + 60 + 12l) \\ 256 \div 2 = 5l + 60 + 12l \\ 128 = 17l + 60 \\ 128 - 60 = 17l \\ 68 = 17l \\ l = 68 \div 17 \\ l = 4$