tolong jawab no 20,21,22,23 pake cara

20) L daerah arsir = ½•π•r²
= ½•3,14•20•20
= 3,14•200
= 628cm²
21) L = ¾•π•r²
= ¾•3,14•40•40
=3•3,14•400
=3,14•1200
=3768 cm²
22) L = ½•π•r² + ½•a•t
= ½•22/7•14•14 + ½•24•36
= 11•28 + 24•18
= 308 + 432
= 740cm²
23) K = π•d + 30 + 30
= 22/7•21 + 60
= 66 + 60
= 126 cm