Comment
There are 4 terms in this series
That's because the summation (Sigma) goes from 3 to 6 inclusive. So k takes on values of 3,4,5,6
You could use this summation formula
Formula
Sum = (a + L)n/2
Substitution
a is the first term.
k = 3 for the first term
a = -5k + 20
a = -5(3) + 20
a = -15 + 20
a = 5
For the last term k = 6
L = -5(6) + 20
L = -30 + 20
L = - 10
Sum
Sum = (5 - 10)*4/2
Sum = -5 * 2
Sum = -10
Comment
You may wonder how come the last term and the sum are the same. The reason to be found by figuring out the 4 terms and adding them together.
When k = 3, -5k + 20 = -15 + 20 = 5
When k = 4, -5k + 20 = -20 + 20 = 0
When k = 5, -5k + 20 = -25 + 20 = -5
When k = 6, -5k + 20 = -30 + 20 = -10
Sum = 5 + 0 - 5 - 10 = - 10
Conclusion.
It is an accident of the numbers.
Answer: - 10 = the Sum
To solve this we need to use Pythagorean theorem

Answer: x≈6.4
ABD is the right triangle. AD is the hypotenuse.
By the <span>Pythagorean theorem:
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<span>
s = 17 units.</span>
Answer:
s=$35n
Step-by-step explanation:
have fun w/ this (also can I get brainiest?)
Answer:
a= 18 girls in the class, b= 20 boys and 15 girls, 12 oranges better price.
Step-by-step explanation:
for question a, there are 18 girls in the class, this is how i worked it out:
the ratio of boys to girls is 4:3.
there are 24 boys.
24 is 6 times more than 4.
if boys are 6 times more than the original ratio, we also have to times the amount of girls by 6.
6x3= 18.
for question b i got 20 boys and 15 girls, this is how i did it.
there are 35 students in total.
4:3= boys to girls.
4+3=7
7 goes into 35 five times.
ratio of boys to girls is 4:3 so 5x4 for boys = 20 and 3x5 for girls = 15.
answer= 20 boys and 15 girls.
12 oranges is a better deal, this is how i worked it out.
it is 60 for 12 oranges.
it is 48 for 8 oranges.
12x5= 60 , 8x6=48.
you only have to times 12 by 5 to get it to the price but you have to times 8 by 6 to get it to the price, proving that 12 oranges for 60 is a better deal.