Question

a lente de uam lupa tem 10 cm de diametro.qual a area da lente desta lupa

Answer 1

D = 2r
10 = 2r
10/2 = r
5 = r
___
A = $\pi$ r²
A = 3,14 x 5²
A = 3,14 x 25
A = 78.5 cm²

Answer 2

$d=10cm\to r=5cm\\\\\\\\A= \pi r^{2} \to\\\\ A=3,14* 5^{2} \to \\\\A=3,14*25\to\\\\\\ A=78,5 cm^{2}$