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Find the sum of the following series by pairing two numbers to make ten(s). 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

Guest Nov 20, 2015

Best Answer 

 #2
avatar+19841 
+15

Find the sum of the following series by pairing two numbers to make ten(s).

1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

 

\( \begin{array}{rcrcrcrcrcrcrcrcrcrcr} \hline \hline 1 &+& 3 &+& 5 &+& 7 &+& 9 &+& 11 &+& 13 &+& 15 &+& 17 &+& 19 & \\ \hline \hline 1 & & & & & & & & & & & & & & & & &+& 19 & =& 20 \\ \hline & & 3 & & & & & & & & & & & & &+& 17 & & & =& 20 \\ \hline & & & & 5 & & & & & & & & &+& 15 & & & & & =& 20 \\ \hline & & & & & & 7 & & & & &+& 13 & & & & & & & =& 20 \\ \hline & & & & & & & & 9 &+& 11 & & & & & & & & & =& 20 \\ \hline \hline & & & & & & & & & & & & & & & & & & & =& 100\\ \hline \hline \end{array}\)

 

( 1 + 19 ) + ( 3 + 17 ) + ( 5 + 15 ) + ( 7 + 13 ) + ( 9 + 11 ) = 20 + 20 + 20 + 20 + 20 = 100

 

laugh

heureka  Nov 20, 2015
edited by heureka  Nov 20, 2015
edited by heureka  Nov 20, 2015
 #1
avatar
+5

(1+9) + (3+7) + (5+15) + (7+13) + (11+19)

10 + 10 + 20 + 20 + 30  = 90

Guest Nov 20, 2015
 #2
avatar+19841 
+15
Best Answer

Find the sum of the following series by pairing two numbers to make ten(s).

1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 + 17 + 19

 

\( \begin{array}{rcrcrcrcrcrcrcrcrcrcr} \hline \hline 1 &+& 3 &+& 5 &+& 7 &+& 9 &+& 11 &+& 13 &+& 15 &+& 17 &+& 19 & \\ \hline \hline 1 & & & & & & & & & & & & & & & & &+& 19 & =& 20 \\ \hline & & 3 & & & & & & & & & & & & &+& 17 & & & =& 20 \\ \hline & & & & 5 & & & & & & & & &+& 15 & & & & & =& 20 \\ \hline & & & & & & 7 & & & & &+& 13 & & & & & & & =& 20 \\ \hline & & & & & & & & 9 &+& 11 & & & & & & & & & =& 20 \\ \hline \hline & & & & & & & & & & & & & & & & & & & =& 100\\ \hline \hline \end{array}\)

 

( 1 + 19 ) + ( 3 + 17 ) + ( 5 + 15 ) + ( 7 + 13 ) + ( 9 + 11 ) = 20 + 20 + 20 + 20 + 20 = 100

 

laugh

heureka  Nov 20, 2015
edited by heureka  Nov 20, 2015
edited by heureka  Nov 20, 2015
 #3
avatar+92922 
0

Two great answers!!

 

What a fabulous diagram Heureka,     laugh

Melody  Nov 20, 2015
 #4
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0

Two great answers, but one of them must be wrong.

The first says 90, the second 100.

Guest Nov 20, 2015
 #5
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0

Yep One of them is wrong....and it's my answer    the answer is 100...I made a typo. The 4th term in my sequence should read (17+13)    NOT   (7 +13)

Guest Nov 21, 2015

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