Question

In a building there are 24 cylindrical pillars with each having a radius 28 cm and height 4 m. Find the cost of painting at a rates of 8 rupees par meter

Answer 1

first take out curved surface area
given
r=28
h=4
curved surface area= 2πrh
2×22/7×0.28×4
7.04cm2
curved surface area of one pillar is 7.04cm2
then curved surface area of 24 pillars =24×704=168.96cm2
cost of painting 168.96×8 RS
1351.68rs

Answer 2

$\huge\tt{Required\:Answer:}$

1. Radius of cylinder pillar (R) => 28cm = 8.28m.
2. Height (h) => 4 m.

$= > Curved \: surface \: area \: of \: pillar = 2\pi \: r \: h \\ = > Curved \: surface \: area \: of \: pillar =2 \times \frac{22}{7} \times 0.28 \times 4 = 7.04 \: m {}^{2} \\ = > Curved \: surface \: area \: of \: 24\: pillar = 7.04 \times 24 = 168.96 \: m {}^{2} \\ = > Cost \: of \: painting \: an \: area \: of \: 1 \: m {}^{2} = 8$

Hence, cost of painting 1689.6 m² = 168.96 × 8 = ₹ 1351.68.