Answer:I think the answer is d
Step-by-step explanation:
Answer:
Step-by-step explanation:
<u>This is going to be an arithmetic progression:</u>
- 48500, 48500 + 1200, 48500 + 1200*2, ...
<u>So the first term is </u>
<u>and the common difference is </u>
<u>Sum of AP is:</u>
- S = (a₁ + aₙ)*n/2 = (2a₁ + (n - 1)d)*n/2
<u>Substitute and solve for n:</u>
- (2*48500 + (n - 1)*1200)*n/2 = 321000
- (97000 + 1200n - 1200)n = 642000
- 1200n² + 95800n - 642000 = 0
- 6n² + 479n - 3210 = 0
<u>Solving we get a positive root of:</u>
- n ≈ 6.21 and it rounds up to 7 years
Answer:
99
Step-by-step explanation:
(40+49)+10=89+10=99
