Answer:
a) 820
b)450
c) -540
d) -294
e) 1440
f) 1425
Step-by-step explanation:
a) it is an arithmetic progression with ratio=4
a1=3,
a2=3+r=3+4=7.....
a20=a1+19r
so a20=3+19*4=3+76=79
S=(a1+an)*n/2 where n=20
so S=(3+79)*20/2=820
b) a15=a1+14*r=2+14*4=2+56=58
S=(a1+a15)*15/2=(2+58)*15/2=60*15/2=30*15=450
It is the same formula for all the exercises
S=(a1+an)*n/2 , where n is the number of terms
c) a40=30+39*(-3)=30-87=-57
So S=(30-57)*40/2=-540
d) a14=5+13*(-4)=5-52=-47
S=(5-47)*14/2=-42*14/2=-42*7=-294
e) it is 5+7+9+......+75
nr of terms = (an-a1) :r+1=(75-5):2+1=36
S=(5+75)*36/2=36*40=1440
f) ratio=7-4=3
the same formula for n= (91-4):3+1=87:3+1=29+1=30
S=(4+91)*30/2=95*30/2=2850/2=1425
Answer:
There are 5 faces, 5 vertices, and 8 edges, so all of that together is 18
Answer:
106 - 8h = 34
Whenever a math question says "when <em>h </em>= 9," they mean you substitute this number where <em>h </em>is in the equation.
106 - 8(9) = 34
106 - 72 = 34
34 = 34
This means the fact that h = 9 <u>is a solution for h.</u>
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1.60 a note book. 6.40\4 assuming they are all the same notebook
Answer:
x = 25 ft
Step-by-step explanation:
here we see the student standing and creating a small triangle that is equivalent to the big triangle since it has the same angles, the only difference is that its smaller, so what we have to do is make a proportion of both triangles, so since 8 ft correspond with the 40 ft they're going to be in the same part of the proportion and the other measurements, including x, on the other part, so itll be 5/8 and x/40, see how the 8 and 40 are both on the bottom? thats because they correspond, so now all you have to do is cross butterfly, so you can set up an expression on 8x= 5*40 or you can just multiply 5*40 and then divide by 8, your answer will be x= 25 ft