Question

Ek golf gend ka vayas 4.1centimetere hai eske prist per 2milimeter ke150gaddhe hai enhai adhra golakar mante hui sampurna pristiye chetrafal nekaliye​

Answer 1

Step-by-step explanation:

Diameter of golf ball = 4.1 cm

$\therefore \: radius \: r = \frac{4.1}{2} = 2.05 \: cm \\ \because \: there \: are \: 150 \: small \: hemispherical \: \\ pits \: on \: the \: surfce \: of \: the \: ball \: each \: of \: \\ 2 \: mm \: depth. \\ \therefore \: radius \: of \: each\: pit \: \\ r_1 = 2 \: mm = 0.2 \: cm \\ now \\ total \: surface \: area \: of \: golf \: ball \\ = 4 \pi \: {r}^{2} + 150 \times \{2\pi \: {r_1}^{2} - \pi \: {r_1}^{2} \} \\ = 4 \pi \: {r}^{2} + 150 \times \pi \: {r_1}^{2 } \\ = 4 \times 3.14 \times (2.05) ^{2} + 150 \times 3.14 \times (0.2)^{2} \\ = 12.56 \times 4.2025 + 471 \times 0.04 \\ = 52.7834 + 18.84 \\ = 71.6234 \: {cm}^{2}$