How much larger is the 8 in 8,237 than the 8 in 823.7?
2 answers:
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Answer:
B.
Step-by-step explanation:
Consider the system of three equations:
Multiply the first equation by 5, the second equation by 2 and subtract them:
Multiply the first equation by 3, the second equation by 2 and subtract them:
Multiply the third equation by 2 and add the second and the third equations:
Fro mthe third equation
Substitute it into the second equation:
Substitute y=20 and z=-14 into the first equation:
The solution is
Answer:
S₁₃ = 455
Step-by-step explanation:
the sum to n terms of an arithmetic is
=
[ 2a₁ + (n - 1)d ]
where a₁ is the first term and d the common difference
We require to find both a₁ and d
The nth term of an arithmetic sequence is
= a₁ + (n - 1)d
given a₄ = 20 and a₁₃ = 65 , then
a₁ + 3d = 20 → (1)
a₁ + 12d = 65 → (2)
subtract (1) from (2) term by term to eliminate a₁
9d = 45 ( divide both sides by 9 )
d = 5
substitute d = 5 into (1) and solve for a₁
a₁ + 3(5) = 20
a₁ + 15 = 20 ( subtract 15 from both sides )
a₁ = 5
Then
S₁₃ = [ (2 × 5 ) + (12 × 5 ) }
= 6.5 (10 + 60)
= 6.5 × 70
= 455