Question

What is the value of 1-2+3-4+5-6.........+19-20??

Answer 1

Answer:

-16

Step-by-step explanation:

1-2+3-4+5-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20

= -1+3-4+5-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20

= -2-4+5-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20

=-6+5-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20

= -1-6+7-8+9-10+11-12+13-14+15-16+17-18+19-20

=-7+7-8+9-10+11-12+13-14+15-16+17-18+19-20

= 0-8+9-10-11-12+13-14+15-16+17-18+19-20

= -8+9-10+11-12+13-14+15-16+17-18+19-20

= -1-10+11-12+13-14+15-16+17-18+19-20

= -11+11-12+13-14+15-16+17-18+19-20

= 0-12+13-14+15-16+17-18+19-20

= -12+13-14+15-16+17-18+19-20

= 1-14+15-16+17-18+19-20

= -13+15-16+17-18+19-20

= 2-16+17-18+19-20

= -14+17-18+19-20

= 3-18+19-20

= -15+19-20

= 4-20

= -16