Question

Add without using number line:
(1) $1+(-7)$ (2) $(-13)+\left(18\right)$
(3) $(-10)+\left(19\right)$ (4) $(-250)+\left(150\right)$
(5) $(-380)+(-270)$ (6) $(-217)+(-100)$

Answer 1

(1) $1+(-7)$

Subtract smaller number from greater : $7-1=6$

As sign of the greater number is '$-$',

So, $1+(-7)=-6$

(2) $(-13)+\left(18\right)$

$13<18$ So, subtracting smaller number from grater, we get $18-13=5$

Since sign of the greater number is '$+$',

So, $(-13)+\left(18\right)=+5$

(3) $(-10)+\left(19\right)$

On similar steps:

as $10<19$, so, $19-10=9$

& sign of $19$ is '$+$',

so, $(-10)+19=+9$

(4) $(-250)+\left(150\right)$

$150<250$ so, $250-150=100$

sign of $250$ is '$-$',

So, $(-250)+150=-100$

(5) $(-280)+(-270)$

sign of both numbers are '$-$', so add them and add a '$-$' sign to the result

$(-380)+(-270)=-(380+270)=-\left(650\right)$

(6) $(-217)+(-100)=-(217+100)=-\left(317\right)$