Answer:
4. 121800
5. 591.09375
6. 0.25
Step-by-step explanation:
4. It's an AP with:
first term(a): 12
common difference(d): 24-18 = 6
Sn = (n/2)(2a + (n-1)d)
S200 = (200/2)[2(12) + (200-1)(6)]
= 121800
5. It's an GP with:
first term(a): 12
common ratio(r): 18/12 = 1.5
Sn= a(r^n -1)/(r-1)
S8 = 12(1.5⁸-1)/(1.5-1)
= 18925/32 = 591.09375
6. It's an infinite GP with:
first term(a) = 1/12
common ratio: 1/18 ÷ 1/12 = ⅔
Sinfinity: a/(1-r)
= (1/12) ÷ [1-⅔]
= 1/12 ÷ 1/3
= 1/12 × 3
= 1/4 = 0.25
