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# Help #3 ​

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Help #3   Mar 12, 2018

#1
+1

Arithmetic sequence with d = 18

26 + 44 + 62 + 80 + 98 + 116 + 134  =        ad 'em up to see what you get !

Or use     SUM =  n ( a1+a7)/2  =    7 (26+134)/2 = ??

4.)  d = 5  so 5n is good..... first one starts with 54 ...no good    second choice only has 13 terms...no good

third choice  starts with 49 and has 5n and has 14 terms.....goood!     Fourth choice has 44 terms....no good

5.

n =1         = 5

2           =6

3             7

4             8         Add 5   6  7   8   and you get ?

Mar 12, 2018

#1
+1

Arithmetic sequence with d = 18

26 + 44 + 62 + 80 + 98 + 116 + 134  =        ad 'em up to see what you get !

Or use     SUM =  n ( a1+a7)/2  =    7 (26+134)/2 = ??

4.)  d = 5  so 5n is good..... first one starts with 54 ...no good    second choice only has 13 terms...no good

third choice  starts with 49 and has 5n and has 14 terms.....goood!     Fourth choice has 44 terms....no good

5.

n =1         = 5

2           =6

3             7

4             8         Add 5   6  7   8   and you get ?

ElectricPavlov Mar 12, 2018
#2
+1

3.

Note NSS  that the distances  are  26, 44, 62, 80.....  each successive term is 18 more than the succeeding one

The 7th term  is

26 +  18 ( 7 - 1)   =   26 + 18 * 6   =  134

For an arithmetic sequence.....the sum is given by :

( First term + Last term ) *  number of terms / 2  =

(26 + 134) * 7 /2    =   160 * 7 / 2   =  160 / 2 * 7   =  80 * 7  =  560 ft

EP's  answer to the second one is good

And for his third answer     5 + 6 + 7 + 8  =

[ 5 + 8] * 4 / 2   =   13 * 2    = 26   Mar 12, 2018