Question by Hương Yêu Dấu - Discuss with MathYouLike

Hương Yêu Dấu

17/09/2017 at 08:38

1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9=?

10 + 20 + 30 + 40 + 50 + 60 +70 + 80 + 90=?

List of answers

18/09/2017 at 05:50

Answer

a, 1 + 2 + 3 + 4 5 + 6 + 7 + 8 + 9

= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) + 5

= 10 + 10 + 10 + 10 + 5

= 40 + 5

=45

b, 10 + 20 + 30 + 40 + 50 + 60 + 70 + 80 + 90

= (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) x 10

= 45 x 10

= 450
Math You Like 17/09/2017 at 08:44

a, 1 + 2 + 3 + 4 5 + 6 + 7 + 8 + 9

= (1 + 9) + (2 + 8) + (3 + 7) + (4 + 6) + 5

= 10 + 10 + 10 + 10 + 5

= 40 + 5

=45

b, 10 + 20 + 30 + 40 + 50 + 60 + 70 + 80 + 90

= (1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9) x 10

= 45 x 10

= 450

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