Question

in a rangoli design of 13 rows every row increases its previous row by two dots and first row contains 5 dots then how many total dots are in the design​

Answer 1

Answer:

there are total 13×2 that is 26 so there are 26dots

Answer 2

Given,

number of rows = 13

number of dots in the 1st row = 5

number of dots increasing per row = 2

To find,

Number of total dots in the design

Solution,

n = 13

a1 = 5

a1, a2, a3 .. = 5, 7, 9

d = 2

Sum = n/2 [2a + (n-1)d]

= 13/2 [2(5) + (13 - 1)(2)]

= 13/2 [10 + 24]

= 13/2 x 34

= 17 x 13

= 221

Thus, there were a total of 221 dots.