The formula for the nth triangular number is n(n+1)/2. Therefore, the fourth triangular number is equal to 4 x (4+1) / 2 = (4 x 5) / 2 = 10. The fiftieth triangular number is equal to 50 x (50+1) / 2 = (50 x 51) / 2 = 1275.
The 20th triangular number is 20*21/2 = 210
yes it is!EDIT: No, it is not.
The 81st triangular number is 3321 The nth triangular number is given by tn = n(n+1) ÷ 2 The 81st triangular number is: t81 = 81(81+1) ÷ 2 = 3321
No. ---- The nth triangular number (n must be a whole number > 0) is given by: tn = 1/2 n(n+1) Testing for 49: 1/2 n(n+1) = 49 → n2 + n - 98 = 0 → n = (-1 ± √393)/2 but 393 is not a square number, so n cannot be a whole number which it must be for a triangular number; thus 49 is not a triangular number.
The formula for the nth triangular number is n(n+1)/2. Therefore, the fourth triangular number is equal to 4 x (4+1) / 2 = (4 x 5) / 2 = 10. The fiftieth triangular number is equal to 50 x (50+1) / 2 = (50 x 51) / 2 = 1275.
The nth triangular number is n(n+1)/2
The nth triangular number is n(n+1)/2
The 20th triangular number is 20*21/2 = 210
The formula for the nth triangular number is n(n+1)/2. If the 8th triangular number is 36, then we can set up the equation 8(8+1)/2 = 36. Solving for n, we get n = 7. Therefore, the 7th triangular number is 7(7+1)/2 = 28.
yes it is!EDIT: No, it is not.
The 81st triangular number is 3321 The nth triangular number is given by tn = n(n+1) ÷ 2 The 81st triangular number is: t81 = 81(81+1) ÷ 2 = 3321
The Nth triangular number is calculated by: N(N + 1) -------- 2 Hope this is useful!
36 is a triangular number. The formula for the nth triangular number is, n(n + 1)/2. So, 36 is the 8th triangular number : 8 x 9/2 = 36
The nth triangular number is n(n+1)/2, so the 2000th triangular number is 2000 * 2001 / 2 = 2,001,000
you need to use this formula: n(n+1) T=--------- 2 So number times (number + 1) divided by 2. If the number you get is the same number as n its a triangular number. if it isn't well it isn't a triangular number.
The nth triangular number is n(n+1)/2