Question

Sum of all even natural numbers less than 85

Answer 1

The series goes like 2,4,6.....84
Sum is given be
$(n (x + y)) \div 2$
where n is the total no. of terms and X is the first term whereas y is the last term.

to find no. of terms.
y=X+(n-1)d
where d is difference between adjacent terms
84=2+(n-1)2
82=(n-1)2
n=42

sum = 42(86)/2


solve and u will get the answer. thanks.

Answer 2

Answer:

Sum of all even natural numbers less than 85 is 1806.

Step-by-step explanation:

• Sequence of even natural number=2,4,6,....84
• First term,a= 2
• Common difference d= 2
• $a_n}$=84
• Number of terms = n
• sum of n terms= $\frac{n}{2 }(first term+last term)$
• nth term $a_n}$=a+(n-1)d

                       $a+(n-1)d=84\\2+(n-1)2=84\\n-1=41\\n=42$

sum of 42 terms= $\frac{n}{2 }(first term+last term)$

                          $=\frac{42}{2} (2+84)\\\\=1806$