Each number in the sum is even, so we can remove a factor of 2.
2 + 4 + 6 + 8 + ... + 78 + 80 = 2 (1 + 2 + 3 + 4 + ... + 39 + 40)
Use whatever technique you used in (a) and (b) to compute the sum
1 + 2 + 3 + 4 + ... + 39 + 40
With Gauss's method, for instance, we have
S = 1 + 2 + 3 + ... + 38 + 39 + 40
S = 40 + 39 + 38 + ... + 3 + 2 + 1
2S = (1 + 40) + (2 + 39) + ... + (39 + 2) + (40 + 1) = 40×41
S = 20×21 = 420
Then the sum you want is 2×420 = 840.
Answer:
x=-7
Step-by-step explanation:
7x2-x=7
7x2=14.
14-x=7
When you finished the last step, you will subtract 14 to both sides.
14-x=7
14-14-x=7-14
this will cancel out the 14 on the left.
And will leave you with:
-x=7-14
7-14 is -7.
and this will get you to
-x=-7
To finish this off, you have to turn the negative x/variable, into a positive x/variable.
So, you will divide both sides of the equation by the same term.
-x = -7
into

and it will be -7.
I hope this helps :)
3 kilometers is equal to 3000 meters
Distance of a ground is 300 meters sou need to run 10 rounds around thefield
Answer:
i think its 6.5
Step-by-step explanation:
42/7 = 6
3/6 = 0.5
6+0.5=6.5