Question

without adding. find the sum (1+2+3+4+5+6+7+8+9​

Answer 1

Answer:

45

Step-by-step explanation:

a=1

l=9

n=9

Sn=(a+l)n/2

=(9+1)×9/2

=10×9/2

=45

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Answer 2

Answer:

45

Step-by-step explanation:

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