Roboguru

Tentukan panjang unsur tabung yang ditanyakan.     Ket: volume tabung, luas permukaan tabung, jari-jari tabung, tinggi tabung.

Pertanyaan

Tentukan panjang unsur tabung yang ditanyakan.

 

 

Ket: undefinedvolume tabung, undefinedluas permukaan tabung, undefinedjari-jari tabung, undefinedtinggi tabung.

Pembahasan Soal:

Diketahui:

Tabung dengan ukuran

begin mathsize 14px style straight L equals 450 straight pi space cm squared straight t equals 15 space cm end style

Ditanya: undefined?

Jawab:

Panjang-jari-jari tabung dapat dicari dengan memanfaatkan luas permukaan tabung.
 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row straight L equals cell 2 πr squared plus 2 πrt end cell row straight L equals cell 2 straight pi left parenthesis straight r squared plus rt right parenthesis end cell row cell stack up diagonal strike 450 straight pi end strike with 225 on top end cell equals cell up diagonal strike 2 straight pi end strike left parenthesis straight r squared plus straight r times 15 right parenthesis end cell row 225 equals cell straight r squared plus 15 straight r end cell row cell straight r squared plus 15 straight r minus 225 end cell equals 0 end table end style
 

Akar-akar persamaan kuadrat perlu dicari dengan rumus begin mathsize 14px style x subscript 1 comma 2 end subscript equals fraction numerator negative b plus-or-minus square root of b squared minus 4 a c end root over denominator 2 a end fraction end style.
 

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell straight r subscript 1 comma 2 end subscript end cell equals cell fraction numerator negative straight b plus-or-minus square root of straight b squared minus 4 ac end root over denominator 2 straight a end fraction end cell row blank equals cell fraction numerator negative 15 plus-or-minus square root of 15 squared minus 4 left parenthesis 1 right parenthesis left parenthesis negative 225 right parenthesis end root over denominator 2 left parenthesis 1 right parenthesis end fraction end cell row blank equals cell fraction numerator negative 15 plus-or-minus square root of 1125 over denominator 2 end fraction end cell row blank equals cell fraction numerator negative 15 plus plus-or-minus square root of 225 times 5 end root over denominator 2 end fraction end cell row blank equals cell fraction numerator negative 15 plus-or-minus 15 square root of 5 over denominator 2 end fraction end cell end table end style

begin mathsize 14px style straight r subscript 1 equals fraction numerator negative 15 plus 15 square root of 5 over denominator 2 end fraction space atau space straight r subscript 2 equals fraction numerator negative 15 minus 15 square root of 5 over denominator 2 end fraction end style
 

Nilai undefined yang mungkin adalah begin mathsize 14px style fraction numerator negative 15 plus 15 square root of 5 over denominator 2 end fraction end style.

Dengan demikian panjang jari-jari tabung adalah undefined cm.

Pembahasan terverifikasi oleh Roboguru

Terakhir diupdate 12 Maret 2021

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