Question

1+2-3+4+5-6+7+8-9+......-48 number series how can i solve

Answer 1

The given expression can be written as
$1 + 2 + 4 + 5... + 46 + 47 \\ - 3 - 6 - 9... - 48 = 1 + 2 + 3 + 4... + 48 \\ - 2 \times (3 + 6 + 9... + 48)$
Since
$1 + 2 + 3...n = n \times( n + 1) \div 2$
the given expression can be simplified as
$(48 \times 49 \div 2) - 2 \times (3 \times 16 \times 17 \div 2)$
which is equal to
$24 \times (49 - 34) = 24 \times 15 = 360$