JAMB - Mathematics (1980 - No. 10)
A solid cylinder of radius 3cm has a total surface area of 36\(\pi\)cm2. Find its height
2cm
3cm
4cm
5cm
6cm
ব্যাখ্যা
Area 2\(\pi\)r2 + 2 \(\pi\)r(r + h)
= 2\(\pi\)r(r + h)
36\(\pi\) = 6\(\pi\)(r + h)
36\(\pi\) = 6\(\pi\)(3 + h)
36\(\pi\) = 18\(\pi\) + 6\(\pi\)h
36\(\pi\) - 18\(\pi\) = 6\(\pi\)h
Divide both side by 6\(\pi\)
h = 3cm
= 2\(\pi\)r(r + h)
36\(\pi\) = 6\(\pi\)(r + h)
36\(\pi\) = 6\(\pi\)(3 + h)
36\(\pi\) = 18\(\pi\) + 6\(\pi\)h
36\(\pi\) - 18\(\pi\) = 6\(\pi\)h
Divide both side by 6\(\pi\)
h = 3cm