Find the sum: 1+2+3+4+ +48+49

For all n, 1 + 2 + + n = n(n + 1)/2, so 1 + 2 + + 49 = 49 50/2 = 1225.

jmc

algebra junior

Problem

Find the sum:

1 + 2 + 3 + 4 + \dots + 48 + 49

Solution

For all

n

1 + 2 + \dots + n = n (n + 1) /2

, so

1 + 2 + \dots + 49 = 49 \cdot 50/2 = 1225

Final answer

1225