Question

7. Which square number will be obtained on adding:
a. 7th and 8th triangular numbers
b. 11th and 12th triangular numbers?​

Answer 1

Step-by-step explanation:

a) 7th triangular number is 36 and 8th triangular number is 45 ,so 36+45=81,perfect square of 9.

b) 11th triangular number is 78 and 12th triangular number is 91, so

78+91=169, perfect square of 13.