The age of james is twice that of Asia. after two years the sum of their ages will be 40 years what are the present ages of jame
1 answer:
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Answer:
a₁ = - 24
Step-by-step explanation:
The n th term of an AP is
= a₁ + (n - 1)d
where a₁ is the first term and d the common difference
Given a₇ = 2a₅ , then
a₁ + 6d = 2(a₁ + 4d) = 2a₁ + 8d ( subtract 2a₁ + 8d from both sides )
- a₁ - 2d = 0 → (1)
The sum to n terms of an AP is
=
[ 2a₁ + (n - 1)d ]
Given = 84 , then
(2a₁ + 6d) = 84
3.5(2a₁ + 6d) = 84 ( divide both sides by 3.5 )
2a₁ + 6d = 24 → (2)
Thus we have 2 equations
- a₁ - 2d = 0 → (1)
2a₁ + 6d = 24 → (2)
Multiplying (1) by 3 and adding to (2) will eliminate d
- 3a₁ - 6d = 0 → (3)
Add (2) and (3) term by term to eliminate d
- a₁ = 24 ( multiply both sides by - 1 )
a₁ = - 24
Answer:
35.4 years
Step-by-step explanation:
The annual consumption (in billions of units) is described by the exponential function ...
f(t) = 45.5·1.026^t
The accumulated consumption is described by the integral ...
We want to find t such that the value of this integral is 2625, the estimated oil reserves.
2625 = 45.5/ln(1.026)·(1.026^t -1)
2625·ln(1.026)/45.5 +1 = 1.026^t ≈ 1.480832 +1 = 1.026^t
Taking natural logs, we have ...
ln(2.480832) = t·ln(1.026)
t ≈ ln(2.480832)/ln(1.026) ≈ 35.398
After about 35.4 years, the oil reserves will run out.
