Question

Find the sum of all multiples of 9 lying between 300 and 700. ​

Answer 1

Answer:

700-300=400 it is not lying between

300

and

700

is

not

proper

no

9

Answer 2

Answer:

21978

Step-by-step explanation:

Multiples of 9 lying between 300 and 700=306,315,324,333,....,693

Here, a=306, d=9 and l=693

We know that, l = a +( n−1 )×d

693 = 306 + ( n−1 ) × 9

( n − 1 ) × 9 = 693 −306 =387

n − 1 = $\frac{387}{9}$ = 43

n = 43 + 1 = 44

There are 44 terms.

Find the sum of 44 terms:

$S_{44}$ = $\frac{n}{2} [a+l ]$

= $\frac{44}{2}[306+693]$

= 22 x 999

= 21978