Find the sum of all positive integers less than $1000$ ending in $3$ or $4$ or $5$.
Note
3 + 4 + 5 = 3 *4
13 + 14 + 15 = 3 * 14...... etc.
3 [ 4 + 14 + 24 + ....... + 994 ] =
No. of terms = 100
Sum = 3 [ 994 + 4 ] [ 100 / 2 ] = 149,700
+1246 
