Jawaban soal aritmatika (A)

           Jawaban soal aritmatika (A)

1.     Jawaban :   B

U_n  = a + ( n – 1 )b

             U₁₀ = a + 9b = 41 

      U₅   = a + 4b = 21  _

5b = 20    → b = 4

a + 4b = 21 → a + 4.4 =21 → a + 16 = 21→ a  =5

U₅₀  = a + ( 50 – 1 )4

        = 5 +  49.4

        = 5 + 196

        = 201           

2.     Jawaban : A

U_n   = S_n – S_{n – 1}

U₂₀ = S₂₀ – S₁₉ = (20² + 5.20) – (19² + 5.19)

  = 500 – 456 = 44

3.     Jawaban : D

Diketahui : a = 120 kg, b = 10 kg, n = 10 bln

 = 1.650 kg

4.     Jawaban : D

U₂ + U₁₅ + U₄₀ = 165

(a + b) + (a + 14b) + (a + 39b) = 165

3a + 54b  = 165 (dibagi 3)

 a + 18b   = 55

Jadi U₁₉  = a + 18b = 55