Chapter 1.1B, Problem 1A

Use the approach in Gauss’s problem to find the following sums of arithmetic sequences.

a. $1+2+3+4+\text{. }\text{. }\text{.+ 49}$

b. $1+3+5+7+\text{. }\text{. }\text{.+ 2009}$

c. $6+12+18+\text{. }\text{. }\text{.+ 600}$

d. $1000+995+900+\text{. }\text{. }\text{.+ 5}$