Number System Practice Test 5

The sum of first n terms of arithmetic series formula can be written as,
Sn=‌

n

2

[2a+(n−1)d]
The list of even numbers between 1 and 50 is 2,4,6,7,8, , .......... 50
Where n= number of terms =?
a= first even number ⇒2 d= common difference of A.P. ⇒2
Tn= Last term ⇒50
Tn=a+(n−1)d
50=2+(n−1)2
50=2+2n−2
50−2+2=2n
50=2n
n=25
Apply the given data in the formula (1),
S25=‌

25

2

[2×2+(25−1)2]
=

25

2

[4+(24)2]
=

25

2

[4+48]
=

25

2

[52]
=25×26
=650

The sum of even numbers from 1 to 50 is 650