त्रिकोणी संख्या
A triangular number is a number that can be represented as a sum of consecutive positive integers starting from
1. The formula to calculate the nth triangular number is Tn = (n(n+1))/2.
Here are the first ten triangular numbers:
T1 = 1
T2 = 3
T3 = 6
T4 = 10
T5 = 15
T6 = 21
T7 = 28
T8 = 36
T9 = 45
T10 = 55
1, 3, 6, 10, 15, 21, 28, 36, 45, 55, 66, 78, 91, 105, 120, 136, 153, 171, 190, 210, 231, 253, 276, 300, 325
Which of the following is a triangular number?
a. 9
b. 14
c. 21
d. 28
Answer: c. 21
What is the fourth triangular number?
a. 6
b. 10
c. 15
d. 21
Answer: b. 10
What is the 10th triangular number?
a. 45
b. 50
c. 55
d. 60
Answer: c. 55
Which of the following is not a triangular number?
a. 16
b. 21
c. 28
d. 36
Answer: a. 16
What is the difference between the 6th and 7th triangular numbers?
a. 6
b. 7
c. 8
d. 9
Answer: b. 7
Which of the following is the 15th triangular number?
a. 105
b. 120
c. 136
d. 153
Answer: b. 120
Which of the following is a triangular number that is also a perfect square?
a. 9
b. 16
c. 25
d. 36
Answer: c. 25
What is the next triangular number after 21?
a. 22
b. 24
c. 28
d. 30
Answer: b. 28
What is the 20th triangular number?
a. 190
b. 200
c. 210
d. 220
Answer: c. 210
What is the sum of the first 10 triangular numbers?
a. 385
b. 450
c. 505
d. 550
Answer: a. 385
What is the difference between the 11th and 12th triangular numbers?
a. 11
b. 12
c. 13
d. 14
Answer: b. 12
What is the 25th triangular number?
a. 300
b. 325
c. 350
d. 375
Answer: b. 325
Which of the following is the largest triangular number less than 100?
a. 45
b. 66
c. 78
d 91
Answer: d. 91
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