Question

Observe the dot arranged in triangles. How many dots will be there in the SEVENTH triangle?

• A. $21$
• B. $24$
• C. $27$
• D. $28$

Answer 1

The correct option is D

$28$

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

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

First number is $1$

Second number is $1+2=3$

Third number is $1+2+3=6$

Similarly, seventh number will be

$1+2+3+4+5+6+7=28$

Hence, the next triangle will have 28 dots.