Find the sum of first five terms of the following series

Find the sum of first five terms of the following series :
1 + 1 + 1 + .......... + .........
1 × 4 4 × 7 7 × 10

From the given question ,

Expression =	1	+	1	+	1	+	1	+	1
	1 × 4		4 × 7		7 × 10		10 × 13		13 × 16

Expression =	1		1 -	1		+	1		1	-	1		......... +	1		1	-	1
	3			4			3		4		7			3		13		16

Expression =	1		1 -	1	+	1	-	1	+	1	-	1	+	1	-	1	+	1	-	1
	3			4		4		7		7		10		10		13		13		16

Expression =	1		1 -	1		Expression =	1	×	15	=	5
	3			16			3		16		16

	1	+	1	+	1	+ .......... + .........
	1 × 4		4 × 7		7 × 10