Answer:
8 days
Step-by-step explanation:
On day 8, Isabella will save 256 nickels, bringing her total to 510.
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The number of nickels saved on day n is 2^n. The total is 2^(n+1)-2.
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The above can be written down from your knowledge of binary sequences. If you want a more formal development, read on.
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The number of nickels saved on day n is a geometric sequence with first term 2 and common ratio 2. The n-th term of the sequence is ...
an = a1·r^(n-1) = 2·2^(n-1) = 2^n
The sum of n terms of the sequence is ...
S = a1(r^n -1)/(r -1) = 2(2^n -1)/(2-1)
S = 2^(n+1) -2
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We want S > 500, so ...
500 < 2^(n+1) -2
502 < 2^(n+1)
251 < 2^n
log(251) < n·log(2)
n > log(251)/log(2)
n > 7.97 . . . . . . . . 8 days or more to save more than 500 nickels
<span>speed = distance/time
total time is 8 hours
outgoing speed is 160 km per hour,
so time = d/160
</span><span>returning speed is 240 km per hour,
so time = d/240
d/160 + d/240 = 8
3d/480 + 2d/480 = 8
5d/480 = 8
5d =480 (8)
5d = 3840
d=3840/5
d=768
answer: so the distance is 768 km</span>
One property of a rhombus is that the diagonals are perpendicular. This means that the diagonals intersect at 90 degree angles (right angles).
So we know that angle JNK is 90 degrees
angle JNK = 90 degrees
5x - 15 = 90
5x - 15 + 15 = 90+15
5x = 105
5x/5 = 105/5
x = 21
Answer: x = 21
ANSWER
B. The two middle coefficients add to the correct number but do not multiply to the correct number.
EXPLANATION
The given quadratic trinomial that Tina tries to factor is
Comparing to
we have a=10, b=-13 and c=-3
ac=-3×10=-30
We split the middle term so that their sum is -13.
Tina use
-10,-3
to get
-10x-3x
The sum is -13x alright but the product is not -30.
B is correct.
Answer:
The first number is 20, the second one is 11
Step-by-step explanation:
Let the first number be x and the second number be y
Since it says "9 is the difference between two numbers", the first equation will be x-y=9
It also says that "their sum is 31". That means the second equation will be x+y=31
here are the two equations:
x-y=9
x+y=31
You can solve this any way you like, but I'll show elimination
add the two equations
x-y=9
x+y=31
2x=40
divide by 2
x=20
Substitute 20 as x in one of the equations
20+y=31
subtract 20 from both sides
y=11
That means the two numbers are 20 and 11
Hope this helps!
