Question

Observe the dot arranged in the triangle. How many dots will be there in the 6th triangle of series?

• A. 19
• B. 18
• C. 23
• D. 21

Answer 1

The correct option is D

21

We can observe that the number of dot in the triangular figure is as follows.

1, 3, 6 ....... and so on

The first number is $1$

The second number is $1+2=3$

The third number is $1+2+3=6$

Similarly, the 6th number will be equal to

$1+2+3+4+5+6=21$

Hence, the next triangle will have 21 dots.