During the seminar, four representatives from institution X, namely Andi, Bowo, Citra, and Dimar, stayed at a hotel and their rooms were located on different floors. Andi had to go down four floors to visit Bowo. Citra's room was one floor below Dimar's room. Bowo had to go down ten floors to get to the restaurant on the 1st floor. Dimar had to go up six floors if he had to meet Andi. What floor was Citra's room on?

Pembahasan

Diketahui bahwa restoran berada di lantai 1 (the restaurant on the 7 st floor). Misal, kamar Andi, Bowo, Citra, dan Dimar menginap masing-masing berada di lantai: A, B, C, dan D. Andi harus turun empat lantai untuk mengunjungi Bowo. Maka: A − 4 = B ... ( 1 ) . Kamar Citra satu lantai di bawah kamar Dimar. Maka: C = D − 1 ... ( 2 ) . Bowo harus turun sepuluh lantai untuk ke restoran yang berada di lantai 1. Maka B − 10 ​ = = ​ 1 11 ... ( 3 ) ​ Dimar harus naik enam lantai jika harus menemui Andi. Maka: D + 6 = A ... ( 4 ) . Dengan mensubstitusikan persamaan ( 3 ) ke persamaan ( 1 ) , maka: A − 4 A ​ = = = ​ 11 11 + 4 15 ​ Substitusikan A = 15 ke persamaan ( 4 ) , maka: D + 6 D ​ = = = ​ 15 15 − 6 9 ​ Substitusikan A = 15 ke persamaan ( 3 ) , maka: C ​ = = ​ 9 − 1 8 ​ Sehingga kamar Citra ada di lantai 8. Oleh karena itu, jawaban yang tepat adalah D.